first commit

core/modules/taxonomy/tests/fixtures/update/remove-description-from-tags-vocabulary.php

@@ -0,0 +1,24 @@
+<?php
+
+/**
+ * @file
+ * Empties the description of the `tags` vocabulary.
+ */
+
+use Drupal\Core\Database\Database;
+
+$connection = Database::getConnection();
+
+$data = $connection->select('config')
+  ->condition('name', 'taxonomy.vocabulary.tags')
+  ->fields('config', ['data'])
+  ->execute()
+  ->fetchField();
+$data = unserialize($data);
+$data['description'] = "\n";
+$connection->update('config')
+  ->condition('name', 'taxonomy.vocabulary.tags')
+  ->fields([
+    'data' => serialize($data),
+  ])
+  ->execute();

core/modules/taxonomy/tests/modules/taxonomy_crud/taxonomy_crud.info.yml

@@ -0,0 +1,12 @@
+name: 'Taxonomy CRUD tests'
+type: module
+description: 'Provides 3rd party settings for vocabulary.'
+package: Testing
+# version: VERSION
+dependencies:
+  - drupal:taxonomy
+
+# Information added by Drupal.org packaging script on 2024-07-04
+version: '10.3.1'
+project: 'drupal'
+datestamp: 1720094222

core/modules/taxonomy/tests/modules/taxonomy_crud/taxonomy_crud.module

@@ -0,0 +1,15 @@
+<?php
+
+/**
+ * @file
+ * Provides hook implementations for testing purposes.
+ */
+
+use Drupal\taxonomy\VocabularyInterface;
+
+/**
+ * Implements hook_ENTITY_TYPE_presave() for taxonomy_vocabulary entities.
+ */
+function taxonomy_crud_taxonomy_vocabulary_presave(VocabularyInterface $vocabulary) {
+  $vocabulary->setThirdPartySetting('taxonomy_crud', 'foo', 'bar');
+}

core/modules/taxonomy/tests/modules/taxonomy_term_display_configurable_test/taxonomy_term_display_configurable_test.info.yml

@@ -0,0 +1,10 @@
+name: 'Taxonomy term configurable display module tests'
+type: module
+description: 'Support module for taxonomy_term \Drupal\Core\Field\BaseFieldDefinition::setDisplayConfigurable() testing.'
+package: Testing
+# version: VERSION
+
+# Information added by Drupal.org packaging script on 2024-07-04
+version: '10.3.1'
+project: 'drupal'
+datestamp: 1720094222

core/modules/taxonomy/tests/modules/taxonomy_term_display_configurable_test/taxonomy_term_display_configurable_test.module

@@ -0,0 +1,26 @@
+<?php
+
+/**
+ * @file
+ * Tests configurable displays for taxonomy_term base fields.
+ */
+
+use Drupal\Core\Entity\EntityTypeInterface;
+
+/**
+ * Implements hook_entity_base_field_info_alter().
+ */
+function taxonomy_term_display_configurable_test_entity_base_field_info_alter(&$base_field_definitions, EntityTypeInterface $entity_type) {
+  if ($entity_type->id() === 'taxonomy_term') {
+    /** @var \Drupal\Core\Field\BaseFieldDefinition[] $base_field_definitions */
+    $base_field_definitions['name']->setDisplayConfigurable('view', TRUE);
+  }
+}
+
+/**
+ * Implements hook_entity_type_build().
+ */
+function taxonomy_term_display_configurable_test_entity_type_build(array &$entity_types) {
+  // Allow skipping of extra preprocessing for configurable display.
+  $entity_types['taxonomy_term']->set('enable_base_field_custom_preprocess_skipping', TRUE);
+}

core/modules/taxonomy/tests/modules/taxonomy_term_stub_test/migrations/taxonomy_term_stub_test.yml

@@ -0,0 +1,32 @@
+id: taxonomy_term_stub_test
+label: Taxonomy term stub
+migration_tags:
+  - Import and rollback test
+source:
+  plugin: embedded_data
+  data_rows:
+    -
+      id: 1
+      vocab: 1
+      name: music
+      parent: 2
+  ids:
+    id:
+      type: integer
+process:
+  tid: id
+  vid: vocab
+  name: name
+  weight: weight
+  parent:
+    plugin: migration_lookup
+    migration: taxonomy_term_stub_test
+    source: parent
+destination:
+  plugin: entity:taxonomy_term
+migration_dependencies:
+  required:
+    - vocabularies
+provider:
+  - migrate_drupal
+  - taxonomy

core/modules/taxonomy/tests/modules/taxonomy_term_stub_test/taxonomy_term_stub_test.info.yml

@@ -0,0 +1,13 @@
+name: 'Taxonomy Migrate stub test'
+type: module
+description: 'Provides a migration plugin for stub testing.'
+package: Testing
+# version: VERSION
+dependencies:
+  - drupal:taxonomy
+  - drupal:migrate
+
+# Information added by Drupal.org packaging script on 2024-07-04
+version: '10.3.1'
+project: 'drupal'
+datestamp: 1720094222

core/modules/taxonomy/tests/modules/taxonomy_test/src/Plugin/views/argument/TaxonomyViewsArgumentTest.php

@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\taxonomy_test\Plugin\views\argument;
+
+use Drupal\Core\Entity\EntityStorageInterface;
+use Drupal\taxonomy\Plugin\views\argument\Taxonomy;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Test argument handler for testing deprecation in Taxonomy argument plugin.
+ *
+ * Intentionally setup our properties and constructor as Drupal 10.2.x and
+ * earlier used in the Taxonomy argument handler.
+ *
+ * @ingroup views_argument_handlers
+ *
+ * @ViewsArgument("taxonomy_views_argument_test")
+ */
+class TaxonomyViewsArgumentTest extends Taxonomy {
+
+  public function __construct(
+    array $configuration,
+    $plugin_id,
+    $plugin_definition,
+    protected EntityStorageInterface $termStorage,
+  ) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition, $termStorage);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('entity_type.manager')->getStorage('taxonomy_term')
+    );
+  }
+
+}

core/modules/taxonomy/tests/modules/taxonomy_test/taxonomy_test.info.yml

@@ -0,0 +1,12 @@
+name: 'Taxonomy test'
+type: module
+description: 'Provides test hook implementations for taxonomy tests'
+package: Testing
+# version: VERSION
+dependencies:
+  - drupal:taxonomy
+
+# Information added by Drupal.org packaging script on 2024-07-04
+version: '10.3.1'
+project: 'drupal'
+datestamp: 1720094222

core/modules/taxonomy/tests/modules/taxonomy_test/taxonomy_test.module

@@ -0,0 +1,60 @@
+<?php
+
+/**
+ * @file
+ * Provides test hook implementations for taxonomy tests.
+ */
+
+use Drupal\Core\Database\Query\AlterableInterface;
+use Drupal\Core\Form\FormStateInterface;
+
+/**
+ * Implements hook_query_alter().
+ */
+function taxonomy_test_query_alter(AlterableInterface $query) {
+  $value = \Drupal::state()->get(__FUNCTION__);
+  if (isset($value)) {
+    \Drupal::state()->set(__FUNCTION__, ++$value);
+  }
+}
+
+/**
+ * Implements hook_query_TAG_alter().
+ */
+function taxonomy_test_query_term_access_alter(AlterableInterface $query) {
+  $value = \Drupal::state()->get(__FUNCTION__);
+  if (isset($value)) {
+    \Drupal::state()->set(__FUNCTION__, ++$value);
+  }
+}
+
+/**
+ * Implements hook_query_TAG_alter().
+ */
+function taxonomy_test_query_taxonomy_term_access_alter(AlterableInterface $query) {
+  $value = \Drupal::state()->get(__FUNCTION__);
+  if (isset($value)) {
+    \Drupal::state()->set(__FUNCTION__, ++$value);
+  }
+}
+
+/**
+ * Implements hook_form_BASE_FORM_ID_alter() for the taxonomy term form.
+ */
+function taxonomy_test_form_taxonomy_term_form_alter(&$form, FormStateInterface $form_state, $form_id) {
+  if (\Drupal::state()->get('taxonomy_test.disable_parent_form_element', FALSE)) {
+    $form['relations']['parent']['#disabled'] = TRUE;
+  }
+}
+
+/**
+ * Implements hook_ENTITY_TYPE_load() for the taxonomy term.
+ */
+function taxonomy_test_taxonomy_term_load($entities) {
+  $value = \Drupal::state()->get(__FUNCTION__);
+  // Only record loaded terms is the test has set this to an empty array.
+  if (is_array($value)) {
+    $value = array_merge($value, array_keys($entities));
+    \Drupal::state()->set(__FUNCTION__, array_unique($value));
+  }
+}

core/modules/taxonomy/tests/modules/taxonomy_test_views/taxonomy_test_views.info.yml

@@ -0,0 +1,13 @@
+name: 'Taxonomy test views'
+type: module
+description: 'Provides default views for views taxonomy tests.'
+package: Testing
+# version: VERSION
+dependencies:
+  - drupal:taxonomy
+  - drupal:views
+
+# Information added by Drupal.org packaging script on 2024-07-04
+version: '10.3.1'
+project: 'drupal'
+datestamp: 1720094222

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.taxonomy_all_terms_test.yml

@@ -0,0 +1,257 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - node
+    - taxonomy
+    - user
+id: taxonomy_all_terms_test
+label: taxonomy_all_terms_test
+module: views
+description: ''
+tag: ''
+base_table: node_field_data
+base_field: nid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: full
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: '‹ Previous'
+            next: 'Next ›'
+            first: '« First'
+            last: 'Last »'
+          quantity: 9
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: fields
+        options:
+          inline: {  }
+          separator: ''
+          hide_empty: false
+          default_field_elements: true
+      fields:
+        term_node_tid:
+          id: term_node_tid
+          table: node_field_data
+          field: term_node_tid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          label: ''
+          exclude: false
+          alter:
+            alter_text: false
+            text: ''
+            make_link: false
+            path: ''
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: false
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          type: separator
+          separator: ', '
+          link_to_taxonomy: true
+          limit: false
+          vids:
+            tags: '0'
+          entity_type: node
+          plugin_id: taxonomy_index_tid
+      filters: {  }
+      sorts:
+        nid:
+          id: nid
+          table: node
+          field: nid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          order: ASC
+          exposed: false
+          expose:
+            label: ''
+          entity_type: node
+          entity_field: nid
+          plugin_id: standard
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments: {  }
+      display_extenders: {  }
+    cache_metadata:
+      contexts:
+        - 'languages:language_interface'
+        - url.query_args
+        - 'user.node_grants:view'
+        - user.permissions
+      max-age: 0
+  page_1:
+    display_plugin: page
+    id: page_1
+    display_title: Page
+    position: 1
+    display_options:
+      display_extenders: {  }
+      path: taxonomy_all_terms_test
+    cache_metadata:
+      contexts:
+        - 'languages:language_interface'
+        - url.query_args
+        - 'user.node_grants:view'
+        - user.permissions
+      cacheable: false
+  page_2:
+    display_plugin: page
+    id: page_2
+    display_title: 'Token tests'
+    position: 2
+    display_options:
+      display_extenders: {  }
+      display_description: ''
+      fields:
+        term_node_tid:
+          id: term_node_tid
+          table: node_field_data
+          field: term_node_tid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          label: ''
+          exclude: false
+          alter:
+            alter_text: true
+            text: "Term: {{ term_node_tid }}<br />\nThe taxonomy term ID for the term: {{ term_node_tid__tid }}<br />\nThe taxonomy term name for the term: {{ term_node_tid__name }}<br />\nThe machine name for the vocabulary the term belongs to: {{ term_node_tid__vocabulary_vid }}<br />\nThe name for the vocabulary the term belongs to: {{ term_node_tid__vocabulary }}<br />"
+            make_link: false
+            path: ''
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: false
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          type: separator
+          separator: '<br />'
+          link_to_taxonomy: false
+          limit: false
+          vids:
+            tags: '0'
+          entity_type: node
+          plugin_id: taxonomy_index_tid
+      defaults:
+        fields: false
+      path: taxonomy_all_terms_token_test
+    cache_metadata:
+      contexts:
+        - 'languages:language_interface'
+        - url.query_args
+        - 'user.node_grants:view'
+        - user.permissions
+      max-age: 0

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.taxonomy_default_argument_test.yml

@@ -0,0 +1,170 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - taxonomy
+    - user
+id: taxonomy_default_argument_test
+label: taxonomy_default_argument_test
+module: views
+description: ''
+tag: ''
+base_table: taxonomy_term_field_data
+base_field: tid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: full
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 20, 40, 60'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: '‹ Previous'
+            next: 'Next ›'
+            first: '« First'
+            last: 'Last »'
+          quantity: 9
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: 'entity:taxonomy_term'
+        options:
+          relationship: none
+          view_mode: default
+      fields:
+        name:
+          id: name
+          table: taxonomy_term_field_data
+          field: name
+          label: ''
+          alter:
+            alter_text: false
+            make_link: false
+            absolute: false
+            trim: false
+            word_boundary: false
+            ellipsis: false
+            strip_tags: false
+            html: false
+          hide_empty: false
+          empty_zero: false
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exclude: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_alter_empty: true
+          plugin_id: field
+          type: string
+          settings:
+            link_to_entity: true
+          entity_type: taxonomy_term
+          entity_field: name
+      filters: {  }
+      sorts: {  }
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments:
+        tid:
+          id: tid
+          table: taxonomy_term_field_data
+          field: tid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          default_action: default
+          exception:
+            value: all
+            title_enable: false
+            title: All
+          title_enable: false
+          title: ''
+          default_argument_type: taxonomy_tid
+          default_argument_options:
+            term_page: '1'
+            node: true
+            anyall: ','
+            limit: false
+            vids: {  }
+          summary_options:
+            base_path: ''
+            count: true
+            items_per_page: 25
+            override: false
+          summary:
+            sort_order: asc
+            number_of_records: 0
+            format: default_summary
+          specify_validation: false
+          validate:
+            type: none
+            fail: 'not found'
+          validate_options: {  }
+          break_phrase: false
+          not: false
+          plugin_id: taxonomy
+          entity_type: taxonomy_term
+          entity_field: tid
+      rendering_language: '***LANGUAGE_entity_translation***'
+  page_1:
+    display_plugin: page
+    id: page_1
+    display_title: Page
+    position: null
+    display_options:
+      path: taxonomy_default_argument_test

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.taxonomy_translated_term_name_test.yml

@@ -0,0 +1,337 @@
+langcode: en
+status: true
+dependencies:
+  config:
+    - core.entity_view_mode.node.teaser
+  module:
+    - node
+    - taxonomy
+    - user
+id: taxonomy_translated_term_name_test
+label: 'Taxonomy Translated Term Name Test'
+module: taxonomy
+description: 'Content belonging to a certain taxonomy term.'
+tag: default
+base_table: node_field_data
+base_field: nid
+display:
+  default:
+    id: default
+    display_title: Default
+    display_plugin: default
+    position: 0
+    display_options:
+      query:
+        type: views_query
+        options:
+          query_comment: ''
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_tags: {  }
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: mini
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: 0
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: ‹‹
+            next: ››
+      sorts:
+        sticky:
+          id: sticky
+          table: taxonomy_index
+          field: sticky
+          order: DESC
+          plugin_id: standard
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exposed: false
+          expose:
+            label: ''
+        created:
+          id: created
+          table: taxonomy_index
+          field: created
+          order: DESC
+          plugin_id: date
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exposed: false
+          expose:
+            label: ''
+          granularity: second
+      arguments:
+        term_node_tid_depth:
+          id: term_node_tid_depth
+          table: node_field_data
+          field: term_node_tid_depth
+          relationship: none
+          group_type: group
+          admin_label: ''
+          default_action: ignore
+          exception:
+            value: all
+            title_enable: false
+            title: All
+          title_enable: true
+          title: '{{ arguments.term_node_tid_depth }}'
+          default_argument_type: fixed
+          default_argument_options:
+            argument: ''
+          summary_options:
+            base_path: ''
+            count: true
+            items_per_page: 25
+            override: false
+          summary:
+            sort_order: asc
+            number_of_records: 0
+            format: default_summary
+          specify_validation: true
+          validate:
+            type: 'entity:taxonomy_term'
+            fail: 'not found'
+          validate_options:
+            access: true
+            operation: view
+            multiple: 0
+            bundles: {  }
+          depth: 2
+          break_phrase: false
+          use_taxonomy_term_path: false
+          entity_type: node
+          plugin_id: taxonomy_index_tid_depth
+      filters:
+        langcode:
+          id: langcode
+          table: node_field_data
+          field: langcode
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: in
+          value:
+            '***LANGUAGE_language_content***': '***LANGUAGE_language_content***'
+          group: 1
+          exposed: false
+          expose:
+            operator_id: ''
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+            reduce: false
+            operator_limit_selection: false
+            operator_list: {  }
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          plugin_id: language
+          entity_type: node
+          entity_field: langcode
+        status:
+          id: status
+          table: taxonomy_index
+          field: status
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: '='
+          value: '1'
+          group: 1
+          exposed: false
+          expose:
+            operator_id: ''
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+            operator_limit_selection: false
+            operator_list: {  }
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          plugin_id: boolean
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: 'entity:node'
+        options:
+          view_mode: teaser
+      header:
+        entity_taxonomy_term:
+          id: entity_taxonomy_term
+          table: views
+          field: entity_taxonomy_term
+          relationship: none
+          group_type: group
+          admin_label: ''
+          empty: true
+          tokenize: true
+          target: '{{ raw_arguments.tid }}'
+          view_mode: full
+          bypass_access: false
+          plugin_id: entity
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      fields: {  }
+      display_extenders: {  }
+      link_url: ''
+      link_display: page_1
+    cache_metadata:
+      contexts:
+        - 'languages:language_interface'
+        - url
+        - url.query_args
+        - 'user.node_grants:view'
+        - user.permissions
+      max-age: -1
+      tags: {  }
+  page_1:
+    id: page_1
+    display_title: Page
+    display_plugin: page
+    position: 1
+    display_options:
+      query:
+        type: views_query
+        options: {  }
+      display_extenders: {  }
+      path: taxonomy/test/%
+    cache_metadata:
+      max-age: -1
+      contexts: {  }
+      tags: {  }
+  page_2:
+    id: page_2
+    display_title: Page
+    display_plugin: page
+    position: 1
+    display_options:
+      arguments:
+        tid:
+          id: tid
+          table: taxonomy_term_field_data
+          field: tid
+          relationship: term_node_tid
+          group_type: group
+          admin_label: ''
+          entity_type: taxonomy_term
+          entity_field: tid
+          plugin_id: taxonomy
+          default_action: ignore
+          exception:
+            value: all
+            title_enable: false
+            title: All
+          title_enable: false
+          title: ''
+          default_argument_type: fixed
+          default_argument_options:
+            argument: ''
+          summary_options:
+            base_path: ''
+            count: true
+            override: false
+            items_per_page: 25
+          summary:
+            sort_order: asc
+            number_of_records: 0
+            format: default_summary
+          specify_validation: false
+          validate:
+            type: none
+            fail: 'not found'
+          validate_options: {  }
+          break_phrase: false
+          not: false
+      query:
+        type: views_query
+        options: {  }
+      defaults:
+        relationships: false
+        arguments: false
+      relationships:
+        term_node_tid:
+          id: term_node_tid
+          table: node_field_data
+          field: term_node_tid
+          relationship: none
+          group_type: group
+          admin_label: term
+          entity_type: node
+          plugin_id: node_term_data
+          required: false
+          vids: {  }
+      display_extenders: {  }
+      path: taxonomy/test2/%
+    cache_metadata:
+      max-age: -1
+      contexts: {  }
+      tags: {  }

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_argument_taxonomy_index_tid_depth.yml

@@ -0,0 +1,225 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - node
+    - taxonomy
+    - user
+id: test_argument_taxonomy_index_tid_depth
+label: test_argument_taxonomy_index_tid_depth
+module: views
+description: ''
+tag: ''
+base_table: node_field_data
+base_field: nid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: full
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: '‹ Previous'
+            next: 'Next ›'
+            first: '« First'
+            last: 'Last »'
+          quantity: 9
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: fields
+        options:
+          inline: {  }
+          separator: ''
+          hide_empty: false
+          default_field_elements: true
+      fields:
+        title:
+          id: title
+          table: node_field_data
+          field: title
+          entity_type: node
+          entity_field: title
+          label: ''
+          alter:
+            alter_text: false
+            make_link: false
+            absolute: false
+            trim: false
+            word_boundary: false
+            ellipsis: false
+            strip_tags: false
+            html: false
+          hide_empty: false
+          empty_zero: false
+          settings:
+            link_to_entity: true
+          plugin_id: field
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exclude: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_alter_empty: true
+          click_sort_column: value
+          type: string
+          group_column: value
+          group_columns: {  }
+          group_rows: true
+          delta_limit: 0
+          delta_offset: 0
+          delta_reversed: false
+          delta_first_last: false
+          multi_type: separator
+          separator: ', '
+          field_api_classes: false
+      filters:
+        status:
+          value: '1'
+          table: node_field_data
+          field: status
+          plugin_id: boolean
+          entity_type: node
+          entity_field: status
+          id: status
+          expose:
+            operator: ''
+          group: 1
+      sorts:
+        created:
+          id: created
+          table: node_field_data
+          field: created
+          order: DESC
+          entity_type: node
+          entity_field: created
+          plugin_id: date
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exposed: false
+          expose:
+            label: ''
+          granularity: second
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments:
+        term_node_tid_depth:
+          id: term_node_tid_depth
+          table: node_field_data
+          field: term_node_tid_depth
+          relationship: none
+          group_type: group
+          admin_label: ''
+          default_action: ignore
+          exception:
+            value: all
+            title_enable: false
+            title: All
+          title_enable: true
+          title: '{{ arguments.term_node_tid_depth }}'
+          default_argument_type: fixed
+          default_argument_options:
+            argument: ''
+          summary_options:
+            base_path: ''
+            count: true
+            items_per_page: 25
+            override: false
+          summary:
+            sort_order: asc
+            number_of_records: 0
+            format: default_summary
+          specify_validation: false
+          validate:
+            type: none
+            fail: 'not found'
+          validate_options: {  }
+          depth: 0
+          break_phrase: false
+          use_taxonomy_term_path: false
+          entity_type: node
+          plugin_id: taxonomy_index_tid_depth
+      display_extenders: {  }
+    cache_metadata:
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url
+        - url.query_args
+        - 'user.node_grants:view'
+        - user.permissions
+      cacheable: false
+  page_1:
+    display_plugin: page
+    id: page_1
+    display_title: Page
+    position: 1
+    display_options:
+      display_extenders: {  }
+      path: test_argument_taxonomy_index_tid_depth
+    cache_metadata:
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url
+        - url.query_args
+        - 'user.node_grants:view'
+        - user.permissions
+      cacheable: false

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_argument_taxonomy_vocabulary.yml

@@ -0,0 +1,171 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - taxonomy
+    - user
+id: test_argument_taxonomy_vocabulary
+label: test_argument_taxonomy_vocabulary
+module: views
+description: ''
+tag: ''
+base_table: taxonomy_term_field_data
+base_field: tid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: none
+        options:
+          offset: 0
+      style:
+        type: default
+      row:
+        type: 'entity:taxonomy_term'
+      fields:
+        name:
+          id: name
+          table: taxonomy_term_field_data
+          field: name
+          entity_type: taxonomy_term
+          entity_field: name
+          label: ''
+          alter:
+            alter_text: false
+            make_link: false
+            absolute: false
+            trim: false
+            word_boundary: false
+            ellipsis: false
+            strip_tags: false
+            html: false
+          hide_empty: false
+          empty_zero: false
+          type: string
+          settings:
+            link_to_entity: true
+          plugin_id: term_name
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exclude: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_alter_empty: true
+          click_sort_column: value
+          group_column: value
+          group_columns: {  }
+          group_rows: true
+          delta_limit: 0
+          delta_offset: 0
+          delta_reversed: false
+          delta_first_last: false
+          multi_type: separator
+          separator: ', '
+          field_api_classes: false
+          convert_spaces: false
+      filters: {  }
+      sorts: {  }
+      title: ''
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments:
+        vid:
+          id: vid
+          table: taxonomy_term_field_data
+          field: vid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          default_action: ignore
+          exception:
+            value: all
+            title_enable: false
+            title: All
+          title_enable: false
+          title: ''
+          default_argument_type: fixed
+          default_argument_options:
+            argument: ''
+          summary_options:
+            base_path: ''
+            count: true
+            items_per_page: 25
+            override: false
+          summary:
+            sort_order: asc
+            number_of_records: 0
+            format: default_summary
+          specify_validation: false
+          validate:
+            type: none
+            fail: 'not found'
+          validate_options: {  }
+          break_phrase: false
+          not: false
+          entity_type: taxonomy_term
+          entity_field: vid
+          plugin_id: vocabulary_vid
+      display_extenders: {  }
+    cache_metadata:
+      max-age: -1
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url
+        - user.permissions
+      tags: {  }
+  page_1:
+    display_plugin: page
+    id: page_1
+    display_title: Page
+    position: 1
+    display_options:
+      display_extenders: {  }
+      path: test_argument_taxonomy_vocabulary
+    cache_metadata:
+      max-age: -1
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url
+        - user.permissions
+      tags: {  }

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_field_filters.yml

@@ -0,0 +1,423 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - taxonomy
+    - user
+id: test_field_filters
+label: 'Test field filters'
+module: views
+description: ''
+tag: ''
+base_table: taxonomy_term_field_data
+base_field: tid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: none
+        options:
+          items_per_page: 0
+          offset: 0
+      style:
+        type: default
+      row:
+        type: 'entity:taxonomy_term'
+      fields:
+        name:
+          id: name
+          table: taxonomy_term_field_data
+          field: name
+          label: ''
+          alter:
+            alter_text: false
+            make_link: false
+            absolute: false
+            trim: false
+            word_boundary: false
+            ellipsis: false
+            strip_tags: false
+            html: false
+          hide_empty: false
+          empty_zero: false
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exclude: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_alter_empty: true
+          plugin_id: field
+          type: string
+          settings:
+            link_to_entity: true
+          entity_type: taxonomy_term
+          entity_field: name
+      filters:
+        name:
+          id: name
+          table: taxonomy_term_field_data
+          field: name
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: contains
+          value: Comida
+          group: 1
+          exposed: false
+          expose:
+            operator_id: ''
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          plugin_id: string
+          entity_type: taxonomy_term
+          entity_field: name
+      sorts: {  }
+      title: 'Name filter page'
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments: {  }
+  page_dc:
+    display_plugin: page
+    id: page_dc
+    display_title: 'Description Comida'
+    position: 3
+    display_options:
+      display_description: ''
+      path: test-desc-filter
+      filters:
+        description__value:
+          id: description__value
+          table: taxonomy_term_field_data
+          field: description__value
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: contains
+          value: Comida
+          group: 1
+          exposed: false
+          expose:
+            operator_id: ''
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          plugin_id: string
+          entity_type: taxonomy_term
+          entity_field: description
+      defaults:
+        filters: false
+        filter_groups: false
+        title: false
+      filter_groups:
+        operator: AND
+        groups:
+          1: AND
+      title: 'Description filter page'
+  page_dp:
+    display_plugin: page
+    id: page_dp
+    display_title: 'Description Comida'
+    position: 3
+    display_options:
+      display_description: ''
+      path: test-desc-paris
+      filters:
+        description__value:
+          id: description__value
+          table: taxonomy_term_field_data
+          field: description__value
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: contains
+          value: Paris
+          group: 1
+          exposed: false
+          expose:
+            operator_id: ''
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          plugin_id: string
+          entity_type: taxonomy_term
+          entity_field: description
+      defaults:
+        filters: false
+        filter_groups: false
+        title: false
+      filter_groups:
+        operator: AND
+        groups:
+          1: AND
+      title: 'Description filter page'
+  page_fc:
+    display_plugin: page
+    id: page_fc
+    display_title: 'Field Comida'
+    position: 3
+    display_options:
+      display_description: ''
+      path: test-field-filter
+      filters:
+        field_foo_value:
+          id: field_foo_value
+          table: taxonomy_term__field_foo
+          field: field_foo_value
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: contains
+          value: Comida
+          group: 1
+          exposed: false
+          expose:
+            operator_id: ''
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          plugin_id: string
+          entity_type: taxonomy_term
+          entity_field: field_foo
+      defaults:
+        filters: false
+        filter_groups: false
+        title: false
+      filter_groups:
+        operator: AND
+        groups:
+          1: AND
+      title: 'Field filter page'
+  page_fp:
+    display_plugin: page
+    id: page_fp
+    display_title: 'Field Paris'
+    position: 3
+    display_options:
+      display_description: ''
+      path: test-field-paris
+      filters:
+        field_foo_value:
+          id: field_foo_value
+          table: taxonomy_term__field_foo
+          field: field_foo_value
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: contains
+          value: Paris
+          group: 1
+          exposed: false
+          expose:
+            operator_id: ''
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          plugin_id: string
+          entity_type: taxonomy_term
+          entity_field: field_foo
+      defaults:
+        filters: false
+        filter_groups: false
+        title: false
+      filter_groups:
+        operator: AND
+        groups:
+          1: AND
+      title: 'Field filter page'
+  page_nc:
+    display_plugin: page
+    id: page_nc
+    display_title: 'Name Comida'
+    position: 1
+    display_options:
+      path: test-name-filter
+      display_description: ''
+  page_np:
+    display_plugin: page
+    id: page_np
+    display_title: 'Name Paris'
+    position: 1
+    display_options:
+      path: test-name-paris
+      display_description: ''
+      filters:
+        name:
+          id: name
+          table: taxonomy_term_field_data
+          field: name
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: contains
+          value: Paris
+          group: 1
+          exposed: false
+          expose:
+            operator_id: ''
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          plugin_id: string
+          entity_type: taxonomy_term
+          entity_field: name
+      defaults:
+        filters: false
+        filter_groups: false
+      filter_groups:
+        operator: AND
+        groups:
+          1: AND

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_filter_taxonomy_index_tid.yml

@@ -0,0 +1,185 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - node
+    - taxonomy
+    - user
+id: test_filter_taxonomy_index_tid
+label: test_filter_taxonomy_index_tid
+module: views
+description: ''
+tag: ''
+base_table: node_field_data
+base_field: nid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 1
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: full
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: '‹ Previous'
+            next: 'Next ›'
+            first: '« First'
+            last: 'Last »'
+          quantity: 9
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: fields
+        options:
+          inline: {  }
+          separator: ''
+          hide_empty: false
+          default_field_elements: true
+      fields:
+        title:
+          id: title
+          table: node_field_data
+          field: title
+          label: ''
+          alter:
+            alter_text: false
+            make_link: false
+            absolute: false
+            trim: false
+            word_boundary: false
+            ellipsis: false
+            strip_tags: false
+            html: false
+          hide_empty: false
+          empty_zero: false
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exclude: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_alter_empty: true
+          plugin_id: field
+          entity_type: node
+          entity_field: title
+      filters:
+        status:
+          value: '1'
+          table: node_field_data
+          field: status
+          id: status
+          expose:
+            operator: '0'
+          group: 1
+          plugin_id: boolean
+          entity_type: node
+          entity_field: status
+        tid:
+          id: tid
+          table: taxonomy_index
+          field: tid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: or
+          value:
+            - 2
+          group: 1
+          exposed: false
+          expose:
+            operator_id: '0'
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+            reduce: false
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          reduce_duplicates: false
+          type: select
+          limit: true
+          vid: tags
+          hierarchy: true
+          error_message: true
+          plugin_id: taxonomy_index_tid
+      sorts: {  }
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments: {  }
+  page_1:
+    display_plugin: page
+    id: page_1
+    display_title: Page
+    position: 2
+    display_options:
+      display_extenders: {  }
+      path: test-filter-taxonomy-index-tid

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_filter_taxonomy_index_tid__non_existing_dependency.yml

@@ -0,0 +1,186 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - node
+    - taxonomy
+    - user
+id: test_filter_taxonomy_index_tid__non_existing_dependency
+label: test_filter_taxonomy_index_tid__non_existing_dependency
+module: views
+description: ''
+tag: ''
+base_table: node_field_data
+base_field: nid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 1
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: full
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: '‹ Previous'
+            next: 'Next ›'
+            first: '« First'
+            last: 'Last »'
+          quantity: 9
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: fields
+        options:
+          inline: {  }
+          separator: ''
+          hide_empty: false
+          default_field_elements: true
+      fields:
+        title:
+          id: title
+          table: node_field_data
+          field: title
+          label: ''
+          alter:
+            alter_text: false
+            make_link: false
+            absolute: false
+            trim: false
+            word_boundary: false
+            ellipsis: false
+            strip_tags: false
+            html: false
+          hide_empty: false
+          empty_zero: false
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exclude: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_alter_empty: true
+          plugin_id: field
+          entity_type: node
+          entity_field: title
+      filters:
+        status:
+          value: '1'
+          table: node_field_data
+          field: status
+          id: status
+          expose:
+            operator: '0'
+          group: 1
+          plugin_id: boolean
+          entity_type: node
+          entity_field: status
+        tid:
+          id: tid
+          table: taxonomy_index
+          field: tid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: or
+          value:
+            - 3
+            - 4
+          group: 1
+          exposed: false
+          expose:
+            operator_id: '0'
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+            reduce: false
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          reduce_duplicates: false
+          type: select
+          limit: true
+          vid: tags
+          hierarchy: true
+          error_message: true
+          plugin_id: taxonomy_index_tid
+      sorts: {  }
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments: {  }
+  page_1:
+    display_plugin: page
+    id: page_1
+    display_title: Page
+    position: 2
+    display_options:
+      display_extenders: {  }
+      path: test-filter-taxonomy-index-tid

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_filter_taxonomy_index_tid_depth.yml

@@ -0,0 +1,192 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - node
+    - taxonomy
+    - user
+id: test_filter_taxonomy_index_tid_depth
+label: test_filter_taxonomy_index_tid_depth
+module: views
+description: ''
+tag: ''
+base_table: node_field_data
+base_field: nid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 1
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: full
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: '‹ Previous'
+            next: 'Next ›'
+            first: '« First'
+            last: 'Last »'
+          quantity: 9
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: fields
+        options:
+          inline: {  }
+          separator: ''
+          hide_empty: false
+          default_field_elements: true
+      fields:
+        title:
+          id: title
+          table: node_field_data
+          field: title
+          label: ''
+          alter:
+            alter_text: false
+            make_link: false
+            absolute: false
+            trim: false
+            word_boundary: false
+            ellipsis: false
+            strip_tags: false
+            html: false
+          hide_empty: false
+          empty_zero: false
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exclude: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_alter_empty: true
+          plugin_id: field
+          entity_type: node
+          entity_field: title
+      filters:
+        status:
+          value: '1'
+          table: node_field_data
+          field: status
+          id: status
+          expose:
+            operator: '0'
+          group: 1
+          plugin_id: boolean
+          entity_type: node
+          entity_field: status
+        tid_depth:
+          id: tid_depth
+          table: node_field_data
+          field: term_node_tid_depth
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: or
+          value: { }
+          group: 1
+          exposed: false
+          expose:
+            operator_id: '0'
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+            reduce: false
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          reduce_duplicates: false
+          type: select
+          limit: true
+          vid: views_testing_tags
+          hierarchy: true
+          depth: -2
+          error_message: true
+          plugin_id: taxonomy_index_tid_depth
+      sorts:
+        created:
+          id: created
+          table: node_field_data
+          field: created
+          order: DESC
+          entity_type: node
+          entity_field: created
+          plugin_id: date
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exposed: false
+          expose:
+            label: ''
+          granularity: second
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments: {  }

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_groupwise_term.yml

@@ -0,0 +1,82 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - node
+    - taxonomy
+    - user
+id: test_groupwise_term
+label: test_groupwise
+module: views
+description: ''
+tag: default
+base_table: taxonomy_term_field_data
+base_field: tid
+display:
+  default:
+    display_options:
+      access:
+        type: perm
+      cache:
+        type: tag
+      exposed_form:
+        type: basic
+      fields:
+        name:
+          field: name
+          id: name
+          table: taxonomy_term_field_data
+          plugin_id: term_name
+          type: string
+          settings:
+            link_to_entity: true
+          convert_spaces: false
+          entity_type: taxonomy_term
+          entity_field: name
+        nid:
+          field: nid
+          id: nid
+          relationship: tid_representative
+          table: node_field_data
+          plugin_id: node
+          entity_type: node
+          entity_field: nid
+      pager:
+        options:
+          items_per_page: 10
+        type: full
+      query:
+        type: views_query
+      relationships:
+        tid_representative:
+          admin_label: 'Representative node'
+          field: tid_representative
+          group_type: group
+          id: tid_representative
+          relationship: none
+          required: false
+          subquery_namespace: ''
+          subquery_order: DESC
+          subquery_regenerate: true
+          subquery_sort: node_field_data.nid
+          subquery_view: ''
+          table: taxonomy_term_field_data
+          plugin_id: groupwise_max
+      row:
+        type: fields
+      sorts:
+        tid:
+          field: tid
+          id: tid
+          order: DESC
+          table: taxonomy_term_field_data
+          plugin_id: standard
+          entity_type: taxonomy_term
+          entity_field: tid
+      style:
+        type: default
+      title: test_groupwise
+    display_plugin: default
+    display_title: Default
+    id: default
+    position: 0

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_taxonomy_exposed_grouped_filter.yml

@@ -0,0 +1,271 @@
+langcode: en
+status: true
+dependencies:
+  config:
+    - node.type.article
+    - taxonomy.vocabulary.tags
+  module:
+    - node
+    - taxonomy
+    - user
+id: test_taxonomy_exposed_grouped_filter
+label: 'Test Taxonomy Exposed Grouped Filter'
+module: views
+description: ''
+tag: ''
+base_table: node_field_data
+base_field: nid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: mini
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: ‹‹
+            next: ››
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: fields
+        options:
+          inline: {  }
+          separator: ''
+          hide_empty: false
+          default_field_elements: true
+      fields:
+        title:
+          id: title
+          table: node_field_data
+          field: title
+          entity_type: node
+          entity_field: title
+          label: ''
+          alter:
+            alter_text: false
+            make_link: false
+            absolute: false
+            trim: false
+            word_boundary: false
+            ellipsis: false
+            strip_tags: false
+            html: false
+          hide_empty: false
+          empty_zero: false
+          settings:
+            link_to_entity: true
+          plugin_id: field
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exclude: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_alter_empty: true
+          click_sort_column: value
+          type: string
+          group_column: value
+          group_columns: {  }
+          group_rows: true
+          delta_limit: 0
+          delta_offset: 0
+          delta_reversed: false
+          delta_first_last: false
+          multi_type: separator
+          separator: ', '
+          field_api_classes: false
+      filters:
+        status:
+          value: '1'
+          table: node_field_data
+          field: status
+          plugin_id: boolean
+          entity_type: node
+          entity_field: status
+          id: status
+          expose:
+            operator: ''
+            operator_limit_selection: false
+            operator_list: {  }
+          group: 1
+        type:
+          id: type
+          table: node_field_data
+          field: type
+          value:
+            article: article
+          entity_type: node
+          entity_field: type
+          plugin_id: bundle
+          expose:
+            operator_limit_selection: false
+            operator_list: {  }
+        field_views_testing_tags_target_id:
+          id: field_views_testing_tags_target_id
+          table: node__field_views_testing_tags
+          field: field_views_testing_tags_target_id
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: or
+          value: {  }
+          group: 1
+          exposed: true
+          expose:
+            operator_id: field_views_testing_tags_target_id_op
+            label: 'views_testing_tags (field_views_testing_tags)'
+            description: null
+            use_operator: false
+            operator: field_views_testing_tags_target_id_op
+            operator_limit_selection: false
+            operator_list: {  }
+            identifier: field_views_testing_tags_target_id
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+            reduce: false
+          is_grouped: true
+          group_info:
+            label: 'views_testing_tags (field_views_testing_tags)'
+            description: ''
+            identifier: field_views_testing_tags_target_id
+            optional: true
+            widget: radios
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items:
+              1:
+                title: 'Group 1'
+                operator: or
+                value:
+                  1: '1'
+                  2: '2'
+              2:
+                title: 'Group 2'
+                operator: or
+                value:
+                  3: '3'
+                  4: '4'
+              3:
+                title: 'Group 3'
+                operator: or
+                value:
+                  1: '1'
+                  5: '5'
+          reduce_duplicates: false
+          type: select
+          limit: true
+          vid: tags
+          hierarchy: false
+          error_message: true
+          plugin_id: taxonomy_index_tid
+      sorts:
+        created:
+          id: created
+          table: node_field_data
+          field: created
+          order: DESC
+          entity_type: node
+          entity_field: created
+          plugin_id: date
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exposed: false
+          expose:
+            label: ''
+            field_identifier: ''
+          granularity: second
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments: {  }
+      display_extenders: {  }
+    cache_metadata:
+      max-age: -1
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url
+        - url.query_args
+        - user
+        - 'user.node_grants:view'
+        - user.permissions
+      tags: {  }
+  page_1:
+    display_plugin: page
+    id: page_1
+    display_title: Page
+    position: 1
+    display_options:
+      display_extenders: {  }
+      path: test-taxonomy-exposed-grouped-filter
+    cache_metadata:
+      max-age: -1
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url
+        - url.query_args
+        - user
+        - 'user.node_grants:view'
+        - user.permissions
+      tags: {  }

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_taxonomy_name_argument.yml

@@ -0,0 +1,234 @@
+langcode: en
+status: true
+dependencies:
+  config:
+    - taxonomy.vocabulary.tags
+  module:
+    - taxonomy
+    - user
+id: test_taxonomy_name_argument
+label: 'Test taxonomy term argument'
+module: views
+description: ''
+tag: ''
+base_table: taxonomy_term_field_data
+base_field: tid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Master
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: mini
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: ‹‹
+            next: ››
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: fields
+        options:
+          inline: {  }
+          separator: ''
+          hide_empty: false
+          default_field_elements: true
+      fields:
+        name:
+          id: name
+          table: taxonomy_term_field_data
+          field: name
+          entity_type: taxonomy_term
+          entity_field: name
+          label: ''
+          alter:
+            alter_text: false
+            make_link: false
+            absolute: false
+            trim: false
+            word_boundary: false
+            ellipsis: false
+            strip_tags: false
+            html: false
+          hide_empty: false
+          empty_zero: false
+          type: string
+          settings:
+            link_to_entity: true
+          plugin_id: term_name
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exclude: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_alter_empty: true
+          click_sort_column: value
+          group_column: value
+          group_columns: {  }
+          group_rows: true
+          delta_limit: 0
+          delta_offset: 0
+          delta_reversed: false
+          delta_first_last: false
+          multi_type: separator
+          separator: ', '
+          field_api_classes: false
+          convert_spaces: false
+      filters:
+        vid:
+          id: vid
+          table: taxonomy_term_field_data
+          field: vid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: in
+          value:
+            tags: tags
+          group: 1
+          exposed: false
+          expose:
+            operator_id: ''
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            operator_limit_selection: false
+            operator_list: {  }
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+            reduce: false
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          entity_type: taxonomy_term
+          entity_field: vid
+          plugin_id: bundle
+      sorts: {  }
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments:
+        name:
+          id: name
+          table: taxonomy_term_field_data
+          field: name
+          relationship: none
+          group_type: group
+          admin_label: ''
+          default_action: ignore
+          exception:
+            value: all
+            title_enable: false
+            title: All
+          title_enable: false
+          title: ''
+          default_argument_type: fixed
+          default_argument_options:
+            argument: ''
+          summary_options:
+            base_path: ''
+            count: true
+            items_per_page: 25
+            override: false
+          summary:
+            sort_order: asc
+            number_of_records: 0
+            format: default_summary
+          specify_validation: true
+          validate:
+            type: taxonomy_term_name
+            fail: 'not found'
+          validate_options:
+            bundles:
+              views_testing_tags: views_testing_tags
+            operation: view
+            access: false
+            transform: false
+          glossary: false
+          limit: 0
+          case: none
+          path_case: none
+          transform_dash: false
+          break_phrase: false
+          add_table: false
+          require_value: false
+          entity_type: taxonomy_term
+          entity_field: name
+          plugin_id: string
+      display_extenders: {  }
+    cache_metadata:
+      max-age: -1
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url
+        - url.query_args
+        - user.permissions
+      tags: {  }

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_taxonomy_node_term_data.yml

@@ -0,0 +1,88 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - node
+    - taxonomy
+    - user
+id: test_taxonomy_node_term_data
+label: test_taxonomy_node_term_data
+module: views
+description: ''
+tag: ''
+base_table: node_field_data
+base_field: nid
+display:
+  default:
+    display_options:
+      access:
+        type: perm
+      arguments:
+        tid:
+          default_argument_type: fixed
+          field: tid
+          id: tid
+          relationship: term_node_tid
+          summary:
+            format: default_summary
+            number_of_records: 0
+          summary_options:
+            items_per_page: 25
+          table: taxonomy_term_field_data
+          plugin_id: taxonomy
+          entity_type: taxonomy_term
+          entity_field: tid
+        tid_1:
+          default_argument_type: fixed
+          field: tid
+          id: tid_1
+          relationship: term_node_tid_1
+          summary:
+            format: default_summary
+            number_of_records: 0
+          summary_options:
+            items_per_page: 25
+          table: taxonomy_term_field_data
+          plugin_id: taxonomy
+          entity_type: taxonomy_term
+          entity_field: tid
+      cache:
+        type: tag
+      exposed_form:
+        type: basic
+      pager:
+        type: full
+      query:
+        type: views_query
+      relationships:
+        term_node_tid:
+          field: term_node_tid
+          id: term_node_tid
+          admin_label: 'Term #1'
+          table: node_field_data
+          vids: {}
+          plugin_id: node_term_data
+        term_node_tid_1:
+          field: term_node_tid
+          id: term_node_tid_1
+          admin_label: 'Term #2'
+          table: node_field_data
+          vids: {}
+          plugin_id: node_term_data
+      sorts:
+        nid:
+          field: nid
+          id: nid
+          order: DESC
+          table: node_field_data
+          plugin_id: standard
+          entity_type: node
+          entity_field: nid
+      style:
+        type: default
+      row:
+        type: 'entity:node'
+    display_plugin: default
+    display_title: Default
+    id: default
+    position: 0

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_taxonomy_parent.yml

@@ -0,0 +1,133 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - taxonomy
+    - user
+id: test_taxonomy_parent
+label: test_taxonomy_parent
+module: views
+description: ''
+tag: ''
+base_table: taxonomy_term_data
+base_field: tid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: full
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: '‹ Previous'
+            next: 'Next ›'
+            first: '« First'
+            last: 'Last »'
+          quantity: 9
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: fields
+        options:
+          inline: {  }
+          separator: ''
+          hide_empty: false
+          default_field_elements: true
+      fields:
+        name:
+          id: name
+          table: taxonomy_term_data
+          field: name
+          label: ''
+          alter:
+            alter_text: false
+            make_link: false
+            absolute: false
+            trim: false
+            word_boundary: false
+            ellipsis: false
+            strip_tags: false
+            html: false
+          hide_empty: false
+          empty_zero: false
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exclude: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_alter_empty: true
+          plugin_id: field
+          type: string
+          settings:
+            link_to_entity: true
+          entity_type: taxonomy_term
+          entity_field: name
+      filters: {  }
+      sorts: {  }
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships:
+        parent:
+          id: parent
+          table: taxonomy_term__parent
+          field: parent_target_id
+          relationship: none
+          group_type: group
+          admin_label: Parent
+          required: true
+          plugin_id: standard
+      arguments: {  }

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_taxonomy_term_name.yml

@@ -0,0 +1,157 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - taxonomy
+    - user
+id: test_taxonomy_term_name
+label: test_taxonomy_term_name
+module: views
+description: ''
+tag: ''
+base_table: taxonomy_term_field_data
+base_field: tid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: full
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 20, 40, 60'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: '‹ Previous'
+            next: 'Next ›'
+            first: '« First'
+            last: 'Last »'
+          quantity: 9
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: fields
+        options:
+          inline: {  }
+          separator: ''
+          hide_empty: false
+          default_field_elements: true
+      fields:
+        name:
+          id: name
+          table: taxonomy_term_field_data
+          field: name
+          relationship: none
+          group_type: group
+          admin_label: ''
+          label: Name
+          exclude: false
+          alter:
+            alter_text: false
+            text: ''
+            make_link: false
+            path: ''
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          plugin_id: term_name
+          type: string
+          settings:
+            link_to_entity: false
+          convert_spaces: false
+          entity_type: taxonomy_term
+          entity_field: name
+      filters: {  }
+      sorts:
+        tid:
+          id: tid
+          table: taxonomy_term_field_data
+          field: tid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          order: ASC
+          exposed: false
+          expose:
+            label: ''
+          plugin_id: standard
+          entity_type: taxonomy_term
+          entity_field: tid
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments: {  }

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_taxonomy_term_relationship.yml

@@ -0,0 +1,201 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - node
+    - taxonomy
+    - user
+id: test_taxonomy_term_relationship
+label: test_taxonomy_term_relationship
+module: views
+description: ''
+tag: ''
+base_table: taxonomy_term_field_data
+base_field: tid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: full
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: '‹ Previous'
+            next: 'Next ›'
+            first: '« First'
+            last: 'Last »'
+          quantity: 9
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: fields
+        options:
+          inline: {  }
+          separator: ''
+          hide_empty: false
+          default_field_elements: true
+      fields:
+        tid:
+          id: tid
+          table: taxonomy_term_field_data
+          field: tid
+          entity_type: taxonomy_term
+          entity_field: tid
+          plugin_id: field
+        tid_1:
+          id: tid_1
+          table: taxonomy_term_field_data
+          field: tid
+          relationship: parent
+          group_type: group
+          admin_label: ''
+          label: ''
+          exclude: false
+          alter:
+            alter_text: false
+            text: ''
+            make_link: false
+            path: ''
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: false
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          click_sort_column: value
+          type: number_integer
+          settings:
+            thousand_separator: ''
+            prefix_suffix: true
+          group_column: value
+          group_columns: {  }
+          group_rows: true
+          delta_limit: 0
+          delta_offset: 0
+          delta_reversed: false
+          delta_first_last: false
+          multi_type: separator
+          separator: ', '
+          field_api_classes: false
+          entity_type: taxonomy_term
+          entity_field: tid
+          plugin_id: field
+        nid:
+          id: nid
+          table: node_field_data
+          field: nid
+          entity_type: node
+          entity_field: nid
+          plugin_id: field
+          relationship: nid
+      filters: {  }
+      sorts:
+        tid:
+          id: tid
+          table: taxonomy_term_field_data
+          field: tid
+          entity_type: taxonomy_term
+          entity_field: tid
+          plugin_id: standard
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships:
+        nid:
+          id: nid
+          table: taxonomy_index
+          field: nid
+          relationship: none
+          group_type: group
+          admin_label: node
+          required: false
+          plugin_id: standard
+        parent:
+          id: parent
+          table: taxonomy_term__parent
+          field: parent_target_id
+          relationship: none
+          group_type: group
+          admin_label: Parent
+          required: false
+          plugin_id: standard
+      arguments: {  }
+      display_extenders: {  }
+    cache_metadata:
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+      max-age: 0

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_taxonomy_tid_field.yml

@@ -0,0 +1,156 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - taxonomy
+    - user
+id: test_taxonomy_tid_field
+label: test_taxonomy_tid_field
+module: views
+description: ''
+tag: ''
+base_table: taxonomy_term_field_data
+base_field: tid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: full
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 20, 40, 60'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: '‹ Previous'
+            next: 'Next ›'
+            first: '« First'
+            last: 'Last »'
+          quantity: 9
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: fields
+        options:
+          inline: {  }
+          separator: ''
+          hide_empty: false
+          default_field_elements: true
+      fields:
+        name:
+          id: name
+          table: taxonomy_term_field_data
+          field: name
+          relationship: none
+          group_type: group
+          admin_label: ''
+          label: Name
+          exclude: false
+          alter:
+            alter_text: false
+            text: ''
+            make_link: false
+            path: ''
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          plugin_id: field
+          type: string
+          settings:
+            link_to_entity: true
+          entity_type: taxonomy_term
+          entity_field: name
+      filters: {  }
+      sorts:
+        tid:
+          id: tid
+          table: taxonomy_term_field_data
+          field: tid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          order: ASC
+          exposed: false
+          expose:
+            label: ''
+          plugin_id: standard
+          entity_type: taxonomy_term
+          entity_field: tid
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments: {  }

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_taxonomy_vid_field.yml

@@ -0,0 +1,177 @@
+uuid: 67bc4e15-f415-4747-8908-d3d56088fbbe
+langcode: en
+status: true
+dependencies:
+  module:
+    - taxonomy
+    - user
+id: test_taxonomy_vid_field
+label: test_taxonomy_vid_field
+module: views
+description: ''
+tag: ''
+base_table: taxonomy_term_field_data
+base_field: tid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: full
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: '‹ Previous'
+            next: 'Next ›'
+            first: '« First'
+            last: 'Last »'
+          quantity: 9
+      style:
+        type: default
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          uses_fields: false
+      row:
+        type: fields
+        options:
+          inline: {  }
+          separator: ''
+          hide_empty: false
+          default_field_elements: true
+      fields:
+        vid:
+          id: vid
+          table: taxonomy_term_field_data
+          field: vid
+          relationship: none
+          group_type: group
+          admin_label: 'Vocabulary name'
+          label: ''
+          exclude: false
+          alter:
+            alter_text: false
+            text: ''
+            make_link: false
+            path: ''
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: false
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          click_sort_column: target_id
+          type: entity_reference_label
+          settings:
+            link: false
+          group_column: target_id
+          group_columns: {  }
+          group_rows: true
+          delta_limit: 0
+          delta_offset: 0
+          delta_reversed: false
+          delta_first_last: false
+          multi_type: separator
+          separator: ', '
+          field_api_classes: false
+          entity_type: taxonomy_term
+          entity_field: vid
+          plugin_id: field
+      filters: {  }
+      sorts:
+        vid:
+          id: vid
+          table: taxonomy_term_field_data
+          field: vid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          order: ASC
+          exposed: false
+          expose:
+            label: ''
+          entity_type: taxonomy_term
+          entity_field: vid
+          plugin_id: standard
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments: {  }
+      display_extenders: {  }
+    cache_metadata:
+      max-age: -1
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url.query_args
+        - user.permissions
+      tags: {  }

core/modules/taxonomy/tests/modules/taxonomy_test_views/test_views/views.view.test_term_show_entity.yml

@@ -0,0 +1,80 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - taxonomy
+id: test_term_show_entity
+label: test_term_show_entity
+module: views
+description: ''
+tag: ''
+base_table: taxonomy_term_field_data
+base_field: tid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: none
+        options: {  }
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: none
+        options:
+          offset: 0
+      style:
+        type: default
+      row:
+        type: 'entity:taxonomy_term'
+      fields: {  }
+      filters: {  }
+      sorts: {  }
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments: {  }
+      display_extenders: {  }
+    cache_metadata:
+      max-age: -1
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+      tags: {  }
+  page_1:
+    display_plugin: page
+    id: page_1
+    display_title: Page
+    position: 1
+    display_options:
+      display_extenders: {  }
+      path: test_term_show_entity
+    cache_metadata:
+      max-age: -1
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+      tags: {  }

core/modules/taxonomy/tests/modules/vocabulary_serialization_test/src/VocabularyResponse.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace Drupal\vocabulary_serialization_test;
+
+use Drupal\Core\Cache\CacheableResponse;
+use Drupal\taxonomy\VocabularyInterface;
+
+class VocabularyResponse extends CacheableResponse {
+
+  /**
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  public function setVocabulary(VocabularyInterface $vocabulary) {
+    $this->vocabulary = $vocabulary;
+  }
+
+}

core/modules/taxonomy/tests/modules/vocabulary_serialization_test/src/VocabularySerializationTestController.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace Drupal\vocabulary_serialization_test;
+
+use Drupal\taxonomy\VocabularyInterface;
+
+class VocabularySerializationTestController {
+
+  public function vocabularyResponse(VocabularyInterface $taxonomy_vocabulary) {
+    $response = new VocabularyResponse('this is the output');
+    $response->setVocabulary($taxonomy_vocabulary);
+    return $response;
+  }
+
+}

core/modules/taxonomy/tests/modules/vocabulary_serialization_test/vocabulary_serialization_test.info.yml

@@ -0,0 +1,11 @@
+name: 'Vocabulary serialization test'
+type: module
+package: Testing
+# version: VERSION
+dependencies:
+  - drupal:taxonomy
+
+# Information added by Drupal.org packaging script on 2024-07-04
+version: '10.3.1'
+project: 'drupal'
+datestamp: 1720094222

core/modules/taxonomy/tests/modules/vocabulary_serialization_test/vocabulary_serialization_test.routing.yml

@@ -0,0 +1,6 @@
+vocabulary_serialization_test:
+  path: '/vocabulary_serialization_test/{taxonomy_vocabulary}'
+  defaults:
+    _controller: '\Drupal\vocabulary_serialization_test\VocabularySerializationTestController::vocabularyResponse'
+  requirements:
+    _access: 'TRUE'

core/modules/taxonomy/tests/src/Functional/EarlyDateTest.php

@@ -0,0 +1,85 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Core\Datetime\DrupalDateTime;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\taxonomy\Entity\Vocabulary;
+
+/**
+ * Posts an article with a taxonomy term and a date prior to 1970.
+ *
+ * @group taxonomy
+ */
+class EarlyDateTest extends TaxonomyTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['node', 'datetime'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    // Create a tags vocabulary for the 'article' content type.
+    $vocabulary = Vocabulary::create([
+      'name' => 'Tags',
+      'vid' => 'tags',
+    ]);
+    $vocabulary->save();
+    $field_name = 'field_' . $vocabulary->id();
+
+    $handler_settings = [
+      'target_bundles' => [
+        $vocabulary->id() => $vocabulary->id(),
+      ],
+      'auto_create' => TRUE,
+    ];
+    $this->createEntityReferenceField('node', 'article', $field_name, 'Tags', 'taxonomy_term', 'default', $handler_settings, FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED);
+
+    \Drupal::service('entity_display.repository')
+      ->getFormDisplay('node', 'article')
+      ->setComponent($field_name, [
+        'type' => 'entity_reference_autocomplete_tags',
+      ])
+      ->save();
+
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer taxonomy',
+      'administer nodes',
+      'bypass node access',
+    ]));
+  }
+
+  /**
+   * Tests taxonomy functionality with nodes prior to 1970.
+   */
+  public function testTaxonomyEarlyDateNode(): void {
+    // Posts an article with a taxonomy term and a date prior to 1970.
+    $date = new DrupalDateTime('1969-01-01 00:00:00');
+    $edit = [];
+    $edit['title[0][value]'] = $this->randomMachineName();
+    $edit['created[0][value][date]'] = $date->format('Y-m-d');
+    $edit['created[0][value][time]'] = $date->format('H:i:s');
+    $edit['body[0][value]'] = $this->randomMachineName();
+    $edit['field_tags[target_id]'] = $this->randomMachineName();
+    $this->drupalGet('node/add/article');
+    $this->submitForm($edit, 'Save');
+    // Checks that the node has been saved.
+    $node = $this->drupalGetNodeByTitle($edit['title[0][value]']);
+    $this->assertEquals($date->getTimestamp(), $node->getCreatedTime(), 'Legacy node was saved with the right date.');
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/GenericTest.php

@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Tests\system\Functional\Module\GenericModuleTestBase;
+
+/**
+ * Generic module test for taxonomy.
+ *
+ * @group taxonomy
+ */
+class GenericTest extends GenericModuleTestBase {}

core/modules/taxonomy/tests/src/Functional/Rest/TermJsonAnonTest.php

@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Tests\rest\Functional\AnonResourceTestTrait;
+
+/**
+ * @group rest
+ * @group #slow
+ */
+class TermJsonAnonTest extends TermResourceTestBase {
+
+  use AnonResourceTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'application/json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/TermJsonBasicAuthTest.php

@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Tests\rest\Functional\BasicAuthResourceTestTrait;
+
+/**
+ * @group rest
+ * @group #slow
+ */
+class TermJsonBasicAuthTest extends TermResourceTestBase {
+
+  use BasicAuthResourceTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['basic_auth'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'application/json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $auth = 'basic_auth';
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/TermJsonCookieTest.php

@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Tests\rest\Functional\CookieResourceTestTrait;
+
+/**
+ * @group rest
+ * @group #slow
+ */
+class TermJsonCookieTest extends TermResourceTestBase {
+
+  use CookieResourceTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'application/json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $auth = 'cookie';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/TermResourceTestBase.php

@@ -0,0 +1,387 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Core\Cache\Cache;
+use Drupal\taxonomy\Entity\Term;
+use Drupal\taxonomy\Entity\Vocabulary;
+use Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase;
+use GuzzleHttp\RequestOptions;
+
+abstract class TermResourceTestBase extends EntityResourceTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['taxonomy', 'path'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $entityTypeId = 'taxonomy_term';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $patchProtectedFieldNames = [
+    'changed' => NULL,
+  ];
+
+  /**
+   * @var \Drupal\taxonomy\TermInterface
+   */
+  protected $entity;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUpAuthorization($method) {
+    switch ($method) {
+      case 'GET':
+        $this->grantPermissionsToTestedRole(['access content']);
+        break;
+
+      case 'POST':
+        $this->grantPermissionsToTestedRole(['create terms in camelids']);
+        break;
+
+      case 'PATCH':
+        // Grant the 'create url aliases' permission to test the case when
+        // the path field is accessible, see
+        // \Drupal\Tests\rest\Functional\EntityResource\Node\NodeResourceTestBase
+        // for a negative test.
+        $this->grantPermissionsToTestedRole(['edit terms in camelids', 'create url aliases']);
+        break;
+
+      case 'DELETE':
+        $this->grantPermissionsToTestedRole(['delete terms in camelids']);
+        break;
+
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function createEntity() {
+    $vocabulary = Vocabulary::load('camelids');
+    if (!$vocabulary) {
+      // Create a "Camelids" vocabulary.
+      $vocabulary = Vocabulary::create([
+        'name' => 'Camelids',
+        'vid' => 'camelids',
+      ]);
+      $vocabulary->save();
+    }
+
+    // Create a "Llama" taxonomy term.
+    $term = Term::create(['vid' => $vocabulary->id()])
+      ->setName('Llama')
+      ->setDescription("It is a little known fact that llamas cannot count higher than seven.")
+      ->setChangedTime(123456789)
+      ->set('path', '/llama');
+    $term->save();
+
+    return $term;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getExpectedNormalizedEntity() {
+    // We test with multiple parent terms, and combinations thereof.
+    // @see ::createEntity()
+    // @see ::testGet()
+    // @see ::testGetTermWithParent()
+    // @see ::providerTestGetTermWithParent()
+    $parent_term_ids = [];
+    for ($i = 0; $i < $this->entity->get('parent')->count(); $i++) {
+      $parent_term_ids[$i] = (int) $this->entity->get('parent')[$i]->target_id;
+    }
+
+    $expected_parent_normalization = FALSE;
+    switch ($parent_term_ids) {
+      case [0]:
+        $expected_parent_normalization = [
+          [
+            'target_id' => NULL,
+          ],
+        ];
+        break;
+
+      case [2]:
+        $expected_parent_normalization = [
+          [
+            'target_id' => 2,
+            'target_type' => 'taxonomy_term',
+            'target_uuid' => Term::load(2)->uuid(),
+            'url' => base_path() . 'taxonomy/term/2',
+          ],
+        ];
+        break;
+
+      case [0, 2]:
+        $expected_parent_normalization = [
+          [
+            'target_id' => NULL,
+          ],
+          [
+            'target_id' => 2,
+            'target_type' => 'taxonomy_term',
+            'target_uuid' => Term::load(2)->uuid(),
+            'url' => base_path() . 'taxonomy/term/2',
+          ],
+        ];
+        break;
+
+      case [3, 2]:
+        $expected_parent_normalization = [
+          [
+            'target_id' => 3,
+            'target_type' => 'taxonomy_term',
+            'target_uuid' => Term::load(3)->uuid(),
+            'url' => base_path() . 'taxonomy/term/3',
+          ],
+          [
+            'target_id' => 2,
+            'target_type' => 'taxonomy_term',
+            'target_uuid' => Term::load(2)->uuid(),
+            'url' => base_path() . 'taxonomy/term/2',
+          ],
+        ];
+        break;
+    }
+
+    return [
+      'tid' => [
+        ['value' => 1],
+      ],
+      'revision_id' => [
+        ['value' => 1],
+      ],
+      'uuid' => [
+        ['value' => $this->entity->uuid()],
+      ],
+      'vid' => [
+        [
+          'target_id' => 'camelids',
+          'target_type' => 'taxonomy_vocabulary',
+          'target_uuid' => Vocabulary::load('camelids')->uuid(),
+        ],
+      ],
+      'name' => [
+        ['value' => 'Llama'],
+      ],
+      'description' => [
+        [
+          'value' => 'It is a little known fact that llamas cannot count higher than seven.',
+          'format' => NULL,
+          'processed' => "<p>It is a little known fact that llamas cannot count higher than seven.</p>\n",
+        ],
+      ],
+      'parent' => $expected_parent_normalization,
+      'weight' => [
+        ['value' => 0],
+      ],
+      'langcode' => [
+        [
+          'value' => 'en',
+        ],
+      ],
+      'changed' => [
+        [
+          'value' => (new \DateTime())->setTimestamp($this->entity->getChangedTime())->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
+      ],
+      'default_langcode' => [
+        [
+          'value' => TRUE,
+        ],
+      ],
+      'path' => [
+        [
+          'alias' => '/llama',
+          'pid' => 1,
+          'langcode' => 'en',
+        ],
+      ],
+      'status' => [
+        [
+          'value' => TRUE,
+        ],
+      ],
+      'revision_created' => [
+        [
+          'value' => (new \DateTime())->setTimestamp((int) $this->entity->getRevisionCreationTime())
+            ->setTimezone(new \DateTimeZone('UTC'))
+            ->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
+      ],
+      'revision_user' => [],
+      'revision_translation_affected' => [
+        [
+          'value' => TRUE,
+        ],
+      ],
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getNormalizedPostEntity() {
+    return [
+      'vid' => [
+        [
+          'target_id' => 'camelids',
+        ],
+      ],
+      'name' => [
+        [
+          'value' => 'Drama llama',
+        ],
+      ],
+      'description' => [
+        [
+          'value' => 'Drama llamas are the coolest camelids.',
+          'format' => NULL,
+        ],
+      ],
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getExpectedUnauthorizedAccessMessage($method) {
+    switch ($method) {
+      case 'GET':
+        return "The 'access content' permission is required and the taxonomy term must be published.";
+
+      case 'POST':
+        return "The following permissions are required: 'create terms in camelids' OR 'administer taxonomy'.";
+
+      case 'PATCH':
+        return "The following permissions are required: 'edit terms in camelids' OR 'administer taxonomy'.";
+
+      case 'DELETE':
+        return "The following permissions are required: 'delete terms in camelids' OR 'administer taxonomy'.";
+
+      default:
+        return parent::getExpectedUnauthorizedAccessMessage($method);
+    }
+  }
+
+  /**
+   * Tests PATCHing a term's path.
+   *
+   * For a negative test, see the similar test coverage for Node.
+   *
+   * @see \Drupal\Tests\rest\Functional\EntityResource\Node\NodeResourceTestBase::testPatchPath()
+   */
+  public function testPatchPath(): void {
+    $this->initAuthentication();
+    $this->provisionEntityResource();
+    $this->setUpAuthorization('GET');
+    $this->setUpAuthorization('PATCH');
+
+    $url = $this->getEntityResourceUrl()->setOption('query', ['_format' => static::$format]);
+
+    // GET term's current normalization.
+    $response = $this->request('GET', $url, $this->getAuthenticationRequestOptions('GET'));
+    $normalization = $this->serializer->decode((string) $response->getBody(), static::$format);
+
+    // Change term's path alias.
+    $normalization['path'][0]['alias'] .= 's-rule-the-world';
+
+    // Create term PATCH request.
+    $request_options = [];
+    $request_options[RequestOptions::HEADERS]['Content-Type'] = static::$mimeType;
+    $request_options = array_merge_recursive($request_options, $this->getAuthenticationRequestOptions('PATCH'));
+    $request_options[RequestOptions::BODY] = $this->serializer->encode($normalization, static::$format);
+
+    // PATCH request: 200.
+    $response = $this->request('PATCH', $url, $request_options);
+    $this->assertResourceResponse(200, FALSE, $response);
+    $updated_normalization = $this->serializer->decode((string) $response->getBody(), static::$format);
+    $this->assertSame($normalization['path'], $updated_normalization['path']);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getExpectedCacheTags() {
+    return Cache::mergeTags(parent::getExpectedCacheTags(), ['config:filter.format.plain_text', 'config:filter.settings']);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getExpectedCacheContexts() {
+    return Cache::mergeContexts(['url.site'], $this->container->getParameter('renderer.config')['required_cache_contexts']);
+  }
+
+  /**
+   * Tests GETting a term with a parent term other than the default <root> (0).
+   *
+   * @see ::getExpectedNormalizedEntity()
+   *
+   * @dataProvider providerTestGetTermWithParent
+   */
+  public function testGetTermWithParent(array $parent_term_ids): void {
+    // Create all possible parent terms.
+    Term::create(['vid' => Vocabulary::load('camelids')->id()])
+      ->setName('Lamoids')
+      ->save();
+    Term::create(['vid' => Vocabulary::load('camelids')->id()])
+      ->setName('Camels')
+      ->save();
+
+    // Modify the entity under test to use the provided parent terms.
+    $this->entity->set('parent', $parent_term_ids)->save();
+
+    $this->initAuthentication();
+    $url = $this->getEntityResourceUrl();
+    $url->setOption('query', ['_format' => static::$format]);
+    $request_options = $this->getAuthenticationRequestOptions('GET');
+    $this->provisionEntityResource();
+    $this->setUpAuthorization('GET');
+    $response = $this->request('GET', $url, $request_options);
+    $expected = $this->getExpectedNormalizedEntity();
+    static::recursiveKSort($expected);
+    $actual = $this->serializer->decode((string) $response->getBody(), static::$format);
+    static::recursiveKSort($actual);
+    $this->assertSame($expected, $actual);
+  }
+
+  public static function providerTestGetTermWithParent() {
+    return [
+      'root parent: [0] (= no parent)' => [
+        [0],
+      ],
+      'non-root parent: [2]' => [
+        [2],
+      ],
+      'multiple parents: [0,2] (root + non-root parent)' => [
+        [0, 2],
+      ],
+      'multiple parents: [3,2] (both non-root parents)' => [
+        [3, 2],
+      ],
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getExpectedUnauthorizedEntityAccessCacheability($is_authenticated) {
+    // @see \Drupal\taxonomy\TermAccessControlHandler::checkAccess()
+    return parent::getExpectedUnauthorizedEntityAccessCacheability($is_authenticated)
+      ->addCacheTags(['taxonomy_term:1']);
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/TermXmlAnonTest.php

@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Tests\rest\Functional\AnonResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrait;
+
+/**
+ * @group rest
+ * @group #slow
+ */
+class TermXmlAnonTest extends TermResourceTestBase {
+
+  use AnonResourceTestTrait;
+  use XmlEntityNormalizationQuirksTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'xml';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'text/xml; charset=UTF-8';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  public function testPatchPath(): void {
+    // Deserialization of the XML format is not supported.
+    $this->markTestSkipped();
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/TermXmlBasicAuthTest.php

@@ -0,0 +1,52 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Tests\rest\Functional\BasicAuthResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrait;
+
+/**
+ * @group rest
+ * @group #slow
+ */
+class TermXmlBasicAuthTest extends TermResourceTestBase {
+
+  use BasicAuthResourceTestTrait;
+  use XmlEntityNormalizationQuirksTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['basic_auth'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'xml';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'text/xml; charset=UTF-8';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $auth = 'basic_auth';
+
+  /**
+   * {@inheritdoc}
+   */
+  public function testPatchPath(): void {
+    // Deserialization of the XML format is not supported.
+    $this->markTestSkipped();
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/TermXmlCookieTest.php

@@ -0,0 +1,47 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Tests\rest\Functional\CookieResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrait;
+
+/**
+ * @group rest
+ * @group #slow
+ */
+class TermXmlCookieTest extends TermResourceTestBase {
+
+  use CookieResourceTestTrait;
+  use XmlEntityNormalizationQuirksTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'xml';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'text/xml; charset=UTF-8';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $auth = 'cookie';
+
+  /**
+   * {@inheritdoc}
+   */
+  public function testPatchPath(): void {
+    // Deserialization of the XML format is not supported.
+    $this->markTestSkipped();
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonAnonTest.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Tests\rest\Functional\AnonResourceTestTrait;
+
+/**
+ * @group rest
+ */
+class VocabularyJsonAnonTest extends VocabularyResourceTestBase {
+
+  use AnonResourceTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'application/json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonBasicAuthTest.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Tests\rest\Functional\BasicAuthResourceTestTrait;
+
+/**
+ * @group rest
+ */
+class VocabularyJsonBasicAuthTest extends VocabularyResourceTestBase {
+
+  use BasicAuthResourceTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['basic_auth'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'application/json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $auth = 'basic_auth';
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonCookieTest.php

@@ -0,0 +1,36 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Tests\rest\Functional\CookieResourceTestTrait;
+
+/**
+ * @group rest
+ */
+class VocabularyJsonCookieTest extends VocabularyResourceTestBase {
+
+  use CookieResourceTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'application/json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $auth = 'cookie';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/VocabularyResourceTestBase.php

@@ -0,0 +1,82 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\taxonomy\Entity\Vocabulary;
+use Drupal\Tests\rest\Functional\EntityResource\ConfigEntityResourceTestBase;
+
+abstract class VocabularyResourceTestBase extends ConfigEntityResourceTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['taxonomy'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $entityTypeId = 'taxonomy_vocabulary';
+
+  /**
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $entity;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUpAuthorization($method) {
+    $this->grantPermissionsToTestedRole(['administer taxonomy']);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function createEntity() {
+    $vocabulary = Vocabulary::create([
+      'name' => 'Llama',
+      'vid' => 'llama',
+    ]);
+    $vocabulary->save();
+
+    return $vocabulary;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getExpectedNormalizedEntity() {
+    return [
+      'uuid' => $this->entity->uuid(),
+      'vid' => 'llama',
+      'langcode' => 'en',
+      'status' => TRUE,
+      'dependencies' => [],
+      'name' => 'Llama',
+      'description' => NULL,
+      'weight' => 0,
+      'new_revision' => FALSE,
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getNormalizedPostEntity() {
+    // @todo Update in https://www.drupal.org/node/2300677.
+    return [];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getExpectedUnauthorizedAccessMessage($method) {
+    if ($method === 'GET') {
+      return "The following permissions are required: 'access taxonomy overview' OR 'administer taxonomy'.";
+    }
+    return parent::getExpectedUnauthorizedAccessMessage($method);
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlAnonTest.php

@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Tests\rest\Functional\AnonResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrait;
+
+/**
+ * @group rest
+ */
+class VocabularyXmlAnonTest extends VocabularyResourceTestBase {
+
+  use AnonResourceTestTrait;
+  use XmlEntityNormalizationQuirksTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'xml';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'text/xml; charset=UTF-8';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlBasicAuthTest.php

@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Tests\rest\Functional\BasicAuthResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrait;
+
+/**
+ * @group rest
+ */
+class VocabularyXmlBasicAuthTest extends VocabularyResourceTestBase {
+
+  use BasicAuthResourceTestTrait;
+  use XmlEntityNormalizationQuirksTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['basic_auth'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'xml';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'text/xml; charset=UTF-8';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $auth = 'basic_auth';
+
+}

core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlCookieTest.php

@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Rest;
+
+use Drupal\Tests\rest\Functional\CookieResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrait;
+
+/**
+ * @group rest
+ */
+class VocabularyXmlCookieTest extends VocabularyResourceTestBase {
+
+  use CookieResourceTestTrait;
+  use XmlEntityNormalizationQuirksTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'xml';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'text/xml; charset=UTF-8';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $auth = 'cookie';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+}

core/modules/taxonomy/tests/src/Functional/RssTest.php

@@ -0,0 +1,148 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\views\Views;
+
+/**
+ * Tests the taxonomy RSS display.
+ *
+ * @group taxonomy
+ */
+class RssTest extends TaxonomyTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['node', 'field_ui', 'views'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Vocabulary for testing.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  /**
+   * Name of the taxonomy term reference field.
+   *
+   * @var string
+   */
+  protected $fieldName;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer taxonomy',
+      'bypass node access',
+      'administer content types',
+      'administer node display',
+    ]));
+    $this->vocabulary = $this->createVocabulary();
+    $this->fieldName = 'taxonomy_' . $this->vocabulary->id();
+
+    $handler_settings = [
+      'target_bundles' => [
+        $this->vocabulary->id() => $this->vocabulary->id(),
+      ],
+      'auto_create' => TRUE,
+    ];
+    $this->createEntityReferenceField('node', 'article', $this->fieldName, NULL, 'taxonomy_term', 'default', $handler_settings, FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED);
+
+    /** @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface $display_repository */
+    $display_repository = \Drupal::service('entity_display.repository');
+
+    $display_repository->getFormDisplay('node', 'article')
+      ->setComponent($this->fieldName, [
+        'type' => 'options_select',
+      ])
+      ->save();
+    $display_repository->getViewDisplay('node', 'article')
+      ->setComponent($this->fieldName, [
+        'type' => 'entity_reference_label',
+      ])
+      ->save();
+  }
+
+  /**
+   * Tests that terms added to nodes are displayed in core RSS feed.
+   *
+   * Create a node and assert that taxonomy terms appear in rss.xml.
+   */
+  public function testTaxonomyRss(): void {
+    // Create two taxonomy terms.
+    $term1 = $this->createTerm($this->vocabulary);
+
+    // Add the RSS display.
+    $default_display = $this->container->get('entity_display.repository')->getViewDisplay('node', 'article');
+    $rss_display = $default_display->createCopy('rss');
+    $rss_display->save();
+
+    // Change the format to 'RSS category'.
+    $rss_display->setComponent('taxonomy_' . $this->vocabulary->id(), [
+      'type' => 'entity_reference_rss_category',
+      'region' => 'content',
+    ]);
+    $rss_display->save();
+
+    // Create an article.
+    $node = $this->drupalCreateNode([
+      'type' => 'article',
+      $this->fieldName => $term1->id(),
+    ]);
+
+    // Check that the term is displayed when the RSS feed is viewed.
+    $this->drupalGet('rss.xml');
+    $test_element = sprintf(
+      '<category %s>%s</category>',
+      'domain="' . $term1->toUrl('canonical', ['absolute' => TRUE])->toString() . '"',
+      $term1->getName()
+    );
+    $this->assertSession()->responseContains($test_element);
+
+    // Test that the feed icon exists for the term.
+    $this->drupalGet("taxonomy/term/{$term1->id()}");
+    $this->assertSession()->linkByHrefExists("taxonomy/term/{$term1->id()}/feed");
+
+    // Test that the feed page exists for the term.
+    $this->drupalGet("taxonomy/term/{$term1->id()}/feed");
+    $assert = $this->assertSession();
+    $assert->responseHeaderContains('Content-Type', 'application/rss+xml');
+    // Ensure the RSS version is 2.0.
+    $rss_array = $this->getSession()->getDriver()->find('rss');
+    $this->assertEquals('2.0', reset($rss_array)->getAttribute('version'));
+
+    // Check that the "Exception value" is disabled by default.
+    $this->drupalGet('taxonomy/term/all/feed');
+    $this->assertSession()->statusCodeEquals(404);
+    // Set the exception value to 'all'.
+    $view = Views::getView('taxonomy_term');
+    $arguments = $view->getDisplay()->getOption('arguments');
+    $arguments['tid']['exception']['value'] = 'all';
+    $view->getDisplay()->overrideOption('arguments', $arguments);
+    $view->storage->save();
+    // Check the article is shown in the feed.
+    $raw_xml = '<title>' . $node->label() . '</title>';
+    $this->drupalGet('taxonomy/term/all/feed');
+    $this->assertSession()->responseContains($raw_xml);
+    // Unpublish the article and check that it is not shown in the feed.
+    $node->setUnpublished()->save();
+    $this->drupalGet('taxonomy/term/all/feed');
+    $this->assertSession()->responseNotContains($raw_xml);
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TaxonomyImageTest.php

@@ -0,0 +1,96 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Tests\TestFileCreationTrait;
+use Drupal\field\Entity\FieldConfig;
+use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\taxonomy\VocabularyInterface;
+
+/**
+ * Tests image upload on taxonomy terms.
+ *
+ * @group taxonomy
+ */
+class TaxonomyImageTest extends TaxonomyTestBase {
+
+  use TestFileCreationTrait {
+    getTestFiles as drupalGetTestFiles;
+    compareFiles as drupalCompareFiles;
+  }
+
+  /**
+   * The taxonomy vocabulary used for the test.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected VocabularyInterface $vocabulary;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['image'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->vocabulary = $this->createVocabulary();
+    $entity_type = 'taxonomy_term';
+    $name = 'field_test';
+    FieldStorageConfig::create([
+      'field_name' => $name,
+      'entity_type' => $entity_type,
+      'type' => 'image',
+    ])->save();
+    FieldConfig::create([
+      'field_name' => $name,
+      'entity_type' => $entity_type,
+      'bundle' => $this->vocabulary->id(),
+      'settings' => [],
+    ])->save();
+    /** @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface $display_repository */
+    $display_repository = \Drupal::service('entity_display.repository');
+    $display_repository->getFormDisplay($entity_type, $this->vocabulary->id())
+      ->setComponent($name, [
+        'type' => 'image_image',
+        'settings' => [],
+      ])
+      ->save();
+  }
+
+  /**
+   * Tests that a file can be uploaded before the taxonomy term has a name.
+   */
+  public function testTaxonomyImageUpload(): void {
+    $user = $this->drupalCreateUser(['administer taxonomy']);
+    $this->drupalLogin($user);
+
+    $files = $this->drupalGetTestFiles('image');
+    $image = array_pop($files);
+
+    // Ensure that a file can be uploaded before taxonomy term has a name.
+    $edit = [
+      'files[field_test_0]' => \Drupal::service('file_system')->realpath($image->uri),
+    ];
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    $this->submitForm($edit, 'Upload');
+
+    $edit = [
+      'name[0][value]' => $this->randomMachineName(),
+      'field_test[0][alt]' => $this->randomMachineName(),
+    ];
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextContains('Created new term');
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TaxonomyRevisionDeleteTest.php

@@ -0,0 +1,112 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+use Drupal\taxonomy\Entity\Term;
+use Drupal\Tests\taxonomy\Traits\TaxonomyTestTrait;
+
+/**
+ * Taxonomy term revision delete form test.
+ *
+ * @group taxonomy
+ * @coversDefaultClass \Drupal\Core\Entity\Form\RevisionDeleteForm
+ */
+class TaxonomyRevisionDeleteTest extends BrowserTestBase {
+
+  use TaxonomyTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'system',
+    'taxonomy',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $permissions = [
+    'view term revisions in test',
+    'delete all taxonomy revisions',
+  ];
+
+  /**
+   * Vocabulary for testing.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  private $vocabulary;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->vocabulary = $this->createVocabulary(['vid' => 'test', 'name' => 'Test']);
+  }
+
+  /**
+   * Tests revision delete.
+   */
+  public function testDeleteForm(): void {
+    $termName = $this->randomMachineName();
+    $entity = Term::create([
+      'vid' => $this->vocabulary->id(),
+      'name' => $termName,
+    ]);
+
+    $entity->setRevisionCreationTime((new \DateTimeImmutable('11 January 2009 4pm'))->getTimestamp())
+      ->setRevisionTranslationAffected(TRUE);
+    $entity->setNewRevision();
+    $entity->save();
+    $revisionId = $entity->getRevisionId();
+
+    $this->drupalLogin($this->drupalCreateUser($this->permissions));
+
+    // Cannot delete latest revision.
+    $this->drupalGet($entity->toUrl('revision-delete-form'));
+    $this->assertSession()->statusCodeEquals(403);
+
+    // Create a new latest revision.
+    $entity
+      ->setRevisionCreationTime((new \DateTimeImmutable('11 January 2009 5pm'))->getTimestamp())
+      ->setRevisionTranslationAffected(TRUE)
+      ->setNewRevision();
+    $entity->save();
+
+    // Reload the entity.
+    $revision = \Drupal::entityTypeManager()->getStorage('taxonomy_term')
+      ->loadRevision($revisionId);
+    $this->drupalGet($revision->toUrl('revision-delete-form'));
+    $this->assertSession()->pageTextContains('Are you sure you want to delete the revision from Sun, 01/11/2009 - 16:00?');
+    $this->assertSession()->buttonExists('Delete');
+    $this->assertSession()->linkExists('Cancel');
+
+    $countRevisions = static function (): int {
+      return (int) \Drupal::entityTypeManager()->getStorage('taxonomy_term')
+        ->getQuery()
+        ->accessCheck(FALSE)
+        ->allRevisions()
+        ->count()
+        ->execute();
+    };
+
+    $count = $countRevisions();
+    $this->submitForm([], 'Delete');
+    $this->assertEquals($count - 1, $countRevisions());
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSession()->addressEquals(sprintf('taxonomy/term/%s/revisions', $entity->id()));
+    $this->assertSession()->pageTextContains(sprintf('Revision from Sun, 01/11/2009 - 16:00 of Test %s has been deleted.', $termName));
+    $this->assertSession()->elementsCount('css', 'table tbody tr', 1);
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TaxonomyRevisionRevertTest.php

@@ -0,0 +1,112 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+use Drupal\taxonomy\Entity\Term;
+use Drupal\Tests\taxonomy\Traits\TaxonomyTestTrait;
+
+/**
+ * Taxonomy term revision form test.
+ *
+ * @group taxonomy
+ * @coversDefaultClass \Drupal\Core\Entity\Form\RevisionRevertForm
+ */
+class TaxonomyRevisionRevertTest extends BrowserTestBase {
+
+  use TaxonomyTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'system',
+    'taxonomy',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $permissions = [
+    'view term revisions in test',
+    'revert all taxonomy revisions',
+  ];
+
+  /**
+   * Vocabulary for testing.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  private $vocabulary;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->vocabulary = $this->createVocabulary(['vid' => 'test', 'name' => 'Test']);
+  }
+
+  /**
+   * Tests revision revert.
+   */
+  public function testRevertForm(): void {
+    $termName = $this->randomMachineName();
+    $entity = Term::create([
+      'vid' => $this->vocabulary->id(),
+      'name' => $termName,
+    ]);
+
+    $entity->setRevisionCreationTime((new \DateTimeImmutable('11 January 2009 4pm'))->getTimestamp())
+      ->setRevisionTranslationAffected(TRUE);
+    $entity->setNewRevision();
+    $entity->save();
+    $revisionId = $entity->getRevisionId();
+
+    $this->drupalLogin($this->drupalCreateUser($this->permissions));
+
+    // Cannot revert latest revision.
+    $this->drupalGet($entity->toUrl('revision-revert-form'));
+    $this->assertSession()->statusCodeEquals(403);
+
+    // Create a new latest revision.
+    $entity
+      ->setRevisionCreationTime((new \DateTimeImmutable('11 January 2009 5pm'))->getTimestamp())
+      ->setRevisionTranslationAffected(TRUE)
+      ->setNewRevision();
+    $entity->save();
+
+    // Reload the entity.
+    $revision = \Drupal::entityTypeManager()->getStorage('taxonomy_term')
+      ->loadRevision($revisionId);
+    $this->drupalGet($revision->toUrl('revision-revert-form'));
+    $this->assertSession()->pageTextContains('Are you sure you want to revert to the revision from Sun, 01/11/2009 - 16:00?');
+    $this->assertSession()->buttonExists('Revert');
+    $this->assertSession()->linkExists('Cancel');
+
+    $countRevisions = static function (): int {
+      return (int) \Drupal::entityTypeManager()->getStorage('taxonomy_term')
+        ->getQuery()
+        ->accessCheck(FALSE)
+        ->allRevisions()
+        ->count()
+        ->execute();
+    };
+
+    $count = $countRevisions();
+    $this->submitForm([], 'Revert');
+    $this->assertEquals($count + 1, $countRevisions());
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSession()->addressEquals(sprintf('taxonomy/term/%s/revisions', $entity->id()));
+    $this->assertSession()->pageTextContains(sprintf('Test %s has been reverted to the revision from Sun, 01/11/2009 - 16:00.', $termName));
+    $this->assertSession()->elementsCount('css', 'table tbody tr', 3);
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TaxonomyRevisionTest.php

@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+use Drupal\Tests\taxonomy\Traits\TaxonomyTestTrait;
+
+/**
+ * Tests the new_revision setting of taxonomy vocabularies.
+ *
+ * @group taxonomy
+ */
+class TaxonomyRevisionTest extends BrowserTestBase {
+
+  use TaxonomyTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'system',
+    'taxonomy',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Tests default revision settings on vocabularies.
+   */
+  public function testVocabularyTermRevision(): void {
+    $assert = $this->assertSession();
+    $vocabulary1 = $this->createVocabulary(['new_revision' => TRUE]);
+    $vocabulary2 = $this->createVocabulary(['new_revision' => FALSE]);
+    $user = $this->createUser([
+      'administer taxonomy',
+    ]);
+    $term1 = $this->createTerm($vocabulary1);
+    $term2 = $this->createTerm($vocabulary2);
+
+    // Create some revisions so revision checkbox is visible.
+    $term1 = $this->createTaxonomyTermRevision($term1);
+    $term2 = $this->createTaxonomyTermRevision($term2);
+    $this->drupalLogin($user);
+    $this->drupalGet($term1->toUrl('edit-form'));
+    $assert->statusCodeEquals(200);
+    $assert->checkboxChecked('Create new revision');
+    $this->drupalGet($term2->toUrl('edit-form'));
+    $assert->statusCodeEquals(200);
+    $assert->checkboxNotChecked('Create new revision');
+
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TaxonomyRevisionVersionHistoryTest.php

@@ -0,0 +1,119 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+use Drupal\taxonomy\Entity\Term;
+use Drupal\Tests\taxonomy\Traits\TaxonomyTestTrait;
+
+/**
+ * Taxonomy term version history test.
+ *
+ * @group taxonomy
+ * @coversDefaultClass \Drupal\Core\Entity\Controller\VersionHistoryController
+ */
+class TaxonomyRevisionVersionHistoryTest extends BrowserTestBase {
+
+  use TaxonomyTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'system',
+    'taxonomy',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $permissions = [
+    'view term revisions in test',
+    'revert all taxonomy revisions',
+    'delete all taxonomy revisions',
+  ];
+
+  /**
+   * Vocabulary for testing.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  private $vocabulary;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->vocabulary = $this->createVocabulary(['vid' => 'test', 'name' => 'Test']);
+  }
+
+  /**
+   * Tests version history page.
+   */
+  public function testVersionHistory(): void {
+    $entity = Term::create([
+      'vid' => $this->vocabulary->id(),
+      'name' => 'Test taxonomy term',
+    ]);
+
+    $entity
+      ->setDescription('Description 1')
+      ->setRevisionCreationTime((new \DateTimeImmutable('1st June 2020 7am'))->getTimestamp())
+      ->setRevisionLogMessage('first revision log')
+      ->setRevisionUser($this->drupalCreateUser(name: 'first author'))
+      ->setNewRevision();
+    $entity->save();
+
+    $entity
+      ->setDescription('Description 2')
+      ->setRevisionCreationTime((new \DateTimeImmutable('2nd June 2020 8am'))->getTimestamp())
+      ->setRevisionLogMessage('second revision log')
+      ->setRevisionUser($this->drupalCreateUser(name: 'second author'))
+      ->setNewRevision();
+    $entity->save();
+
+    $entity
+      ->setDescription('Description 3')
+      ->setRevisionCreationTime((new \DateTimeImmutable('3rd June 2020 9am'))->getTimestamp())
+      ->setRevisionLogMessage('third revision log')
+      ->setRevisionUser($this->drupalCreateUser(name: 'third author'))
+      ->setNewRevision();
+    $entity->save();
+
+    $this->drupalLogin($this->drupalCreateUser($this->permissions));
+    $this->drupalGet($entity->toUrl('version-history'));
+    $this->assertSession()->elementsCount('css', 'table tbody tr', 3);
+
+    // Order is newest to oldest revision by creation order.
+    $row1 = $this->assertSession()->elementExists('css', 'table tbody tr:nth-child(1)');
+    // Latest revision does not have revert or delete revision operation.
+    $this->assertSession()->elementNotExists('named', ['link', 'Revert'], $row1);
+    $this->assertSession()->elementNotExists('named', ['link', 'Delete'], $row1);
+    $this->assertSession()->elementTextContains('css', 'table tbody tr:nth-child(1)', 'Current revision');
+    $this->assertSession()->elementTextContains('css', 'table tbody tr:nth-child(1)', 'third revision log');
+    $this->assertSession()->elementTextContains('css', 'table tbody tr:nth-child(1)', '06/03/2020 - 09:00 by third author');
+
+    $row2 = $this->assertSession()->elementExists('css', 'table tbody tr:nth-child(2)');
+    $this->assertSession()->elementExists('named', ['link', 'Revert'], $row2);
+    $this->assertSession()->elementExists('named', ['link', 'Delete'], $row2);
+    $this->assertSession()->elementTextNotContains('css', 'table tbody tr:nth-child(2)', 'Current revision');
+    $this->assertSession()->elementTextContains('css', 'table tbody tr:nth-child(2)', 'second revision log');
+    $this->assertSession()->elementTextContains('css', 'table tbody tr:nth-child(2)', '06/02/2020 - 08:00 by second author');
+
+    $row3 = $this->assertSession()->elementExists('css', 'table tbody tr:nth-child(3)');
+    $this->assertSession()->elementExists('named', ['link', 'Revert'], $row3);
+    $this->assertSession()->elementExists('named', ['link', 'Delete'], $row3);
+    $this->assertSession()->elementTextNotContains('css', 'table tbody tr:nth-child(2)', 'Current revision');
+    $this->assertSession()->elementTextContains('css', 'table tbody tr:nth-child(3)', 'first revision log');
+    $this->assertSession()->elementTextContains('css', 'table tbody tr:nth-child(3)', '06/01/2020 - 07:00 by first author');
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TaxonomyTermContentModerationTest.php

@@ -0,0 +1,217 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Core\Url;
+use Drupal\Tests\content_moderation\Traits\ContentModerationTestTrait;
+use Drupal\workflows\Entity\Workflow;
+
+/**
+ * Tests taxonomy terms with Content Moderation.
+ *
+ * @group content_moderation
+ * @group taxonomy
+ */
+class TaxonomyTermContentModerationTest extends TaxonomyTestBase {
+
+  use ContentModerationTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * The vocabulary used for creating terms.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['content_moderation'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->createEditorialWorkflow();
+
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer taxonomy',
+      'use editorial transition create_new_draft',
+      'use editorial transition publish',
+      'view any unpublished content',
+      'view latest version',
+    ]));
+
+    $this->vocabulary = $this->createVocabulary();
+
+    // Set the vocabulary as moderated.
+    $workflow = Workflow::load('editorial');
+    $workflow->getTypePlugin()->addEntityTypeAndBundle('taxonomy_term', $this->vocabulary->id());
+    $workflow->save();
+  }
+
+  /**
+   * Tests taxonomy term parents on a moderated vocabulary.
+   */
+  public function testTaxonomyTermParents(): void {
+    $assert_session = $this->assertSession();
+    // Create a simple hierarchy in the vocabulary, a root term and three parent
+    // terms.
+    $root = $this->createTerm($this->vocabulary, ['langcode' => 'en', 'moderation_state' => 'published']);
+    $parent_1 = $this->createTerm($this->vocabulary, [
+      'langcode' => 'en',
+      'moderation_state' => 'published',
+      'parent' => $root->id(),
+    ]);
+    $parent_2 = $this->createTerm($this->vocabulary, [
+      'langcode' => 'en',
+      'moderation_state' => 'published',
+      'parent' => $root->id(),
+    ]);
+    $parent_3 = $this->createTerm($this->vocabulary, [
+      'langcode' => 'en',
+      'moderation_state' => 'published',
+      'parent' => $root->id(),
+    ]);
+
+    // Create a child term and assign one of the parents above.
+    $child = $this->createTerm($this->vocabulary, [
+      'langcode' => 'en',
+      'moderation_state' => 'published',
+      'parent' => $parent_1->id(),
+    ]);
+
+    /** @var \Drupal\taxonomy\TermStorageInterface $taxonomy_storage */
+    $taxonomy_storage = \Drupal::entityTypeManager()->getStorage('taxonomy_term');
+    $validation_message = 'You can only change the hierarchy for the published version of this term.';
+
+    // Add a pending revision without changing the term parent.
+    $this->drupalGet($child->toUrl('edit-form'));
+    $this->submitForm(['moderation_state[0][state]' => 'draft'], 'Save');
+
+    $assert_session->pageTextNotContains($validation_message);
+
+    // Add a pending revision and change the parent.
+    $this->drupalGet($child->toUrl('edit-form'));
+    $this->submitForm(['parent[]' => [$parent_2->id()], 'moderation_state[0][state]' => 'draft'], 'Save');
+
+    // Check that parents were not changed.
+    $assert_session->pageTextContains($validation_message);
+    $taxonomy_storage->resetCache();
+    $this->assertEquals([$parent_1->id()], array_keys($taxonomy_storage->loadParents($child->id())));
+
+    // Add a pending revision and add a new parent.
+    $this->drupalGet($child->toUrl('edit-form'));
+    $this->submitForm(['parent[]' => [$parent_1->id(), $parent_3->id()], 'moderation_state[0][state]' => 'draft'], 'Save');
+
+    // Check that parents were not changed.
+    $assert_session->pageTextContains($validation_message);
+    $taxonomy_storage->resetCache();
+    $this->assertEquals([$parent_1->id()], array_keys($taxonomy_storage->loadParents($child->id())));
+
+    // Add a pending revision and use the root term as a parent.
+    $this->drupalGet($child->toUrl('edit-form'));
+    $this->submitForm(['parent[]' => [$root->id()], 'moderation_state[0][state]' => 'draft'], 'Save');
+
+    // Check that parents were not changed.
+    $assert_session->pageTextContains($validation_message);
+    $taxonomy_storage->resetCache();
+    $this->assertEquals([$parent_1->id()], array_keys($taxonomy_storage->loadParents($child->id())));
+
+    // Add a pending revision and remove the parent.
+    $this->drupalGet($child->toUrl('edit-form'));
+    $this->submitForm(['parent[]' => [], 'moderation_state[0][state]' => 'draft'], 'Save');
+
+    // Check that parents were not changed.
+    $assert_session->pageTextContains($validation_message);
+    $taxonomy_storage->resetCache();
+    $this->assertEquals([$parent_1->id()], array_keys($taxonomy_storage->loadParents($child->id())));
+
+    // Add a published revision.
+    $this->drupalGet($child->toUrl('edit-form'));
+    $this->submitForm(['moderation_state[0][state]' => 'published'], 'Save');
+
+    // Change the parents.
+    $this->drupalGet($child->toUrl('edit-form'));
+    $this->submitForm(['parent[]' => [$parent_2->id()]], 'Save');
+
+    // Check that parents were changed.
+    $assert_session->pageTextNotContains($validation_message);
+    $taxonomy_storage->resetCache();
+    $this->assertNotEquals([$parent_1->id()], array_keys($taxonomy_storage->loadParents($child->id())));
+
+    // Add a pending revision and change the weight.
+    $this->drupalGet($child->toUrl('edit-form'));
+    $this->submitForm(['weight' => 10, 'moderation_state[0][state]' => 'draft'], 'Save');
+
+    // Check that weight was not changed.
+    $assert_session->pageTextContains($validation_message);
+
+    // Add a new term without any parent and publish it.
+    $edit = [
+      'name[0][value]' => $this->randomMachineName(),
+      'moderation_state[0][state]' => 'published',
+    ];
+    $this->drupalGet(Url::fromRoute('entity.taxonomy_term.add_form', ['taxonomy_vocabulary' => $this->vocabulary->id()]));
+    $this->submitForm($edit, 'Save');
+    // Add a pending revision without any changes.
+    $terms = \Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadByProperties(['name' => $edit['name[0][value]']]);
+    $term = reset($terms);
+    $this->drupalGet($term->toUrl('edit-form'));
+    $this->submitForm(['moderation_state[0][state]' => 'draft'], 'Save');
+    $assert_session->pageTextNotContains($validation_message);
+  }
+
+  /**
+   * Tests changing field values in pending revisions of taxonomy terms.
+   */
+  public function testTaxonomyTermPendingRevisions(): void {
+    $assert_session = $this->assertSession();
+    $default_term_name = 'term - default revision';
+    $default_term_description = 'The default revision of a term.';
+    $term = $this->createTerm($this->vocabulary, [
+      'name' => $default_term_name,
+      'description' => $default_term_description,
+      'langcode' => 'en',
+      'moderation_state' => 'published',
+    ]);
+
+    // Add a pending revision without changing the term parent.
+    $this->drupalGet($term->toUrl('edit-form'));
+    $assert_session->pageTextContains($default_term_name);
+    $assert_session->pageTextContains($default_term_description);
+
+    // Check the revision log message field appears on the term edit page.
+    $this->drupalGet($term->toUrl('edit-form'));
+    $assert_session->fieldExists('revision_log_message[0][value]');
+
+    $pending_term_name = 'term - pending revision';
+    $pending_term_description = 'The pending revision of a term.';
+    $edit = [
+      'name[0][value]' => $pending_term_name,
+      'description[0][value]' => $pending_term_description,
+      'moderation_state[0][state]' => 'draft',
+    ];
+    $this->drupalGet($term->toUrl('edit-form'));
+    $this->submitForm($edit, 'Save');
+
+    $assert_session->pageTextContains($pending_term_name);
+    $assert_session->pageTextContains($pending_term_description);
+    $assert_session->pageTextNotContains($default_term_description);
+
+    // Check that the default revision of the term contains the correct values.
+    $this->drupalGet('taxonomy/term/' . $term->id());
+    $assert_session->pageTextContains($default_term_name);
+    $assert_session->pageTextContains($default_term_description);
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TaxonomyTermIndentationTest.php

@@ -0,0 +1,108 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+/**
+ * Ensure that the term indentation works properly.
+ *
+ * @group taxonomy
+ */
+class TaxonomyTermIndentationTest extends TaxonomyTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['taxonomy'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Vocabulary for testing.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer taxonomy',
+      'bypass node access',
+    ]));
+    $this->vocabulary = $this->createVocabulary();
+  }
+
+  /**
+   * Tests term indentation.
+   */
+  public function testTermIndentation(): void {
+    $assert = $this->assertSession();
+    // Create three taxonomy terms.
+    $term1 = $this->createTerm($this->vocabulary);
+    $term2 = $this->createTerm($this->vocabulary);
+    $term3 = $this->createTerm($this->vocabulary);
+
+    // Get the taxonomy storage.
+    $taxonomy_storage = $this->container->get('entity_type.manager')->getStorage('taxonomy_term');
+
+    // Indent the second term under the first one.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->get('vid') . '/overview');
+    $hidden_edit = [
+      'terms[tid:' . $term2->id() . ':0][term][tid]' => 2,
+      'terms[tid:' . $term2->id() . ':0][term][parent]' => 1,
+      'terms[tid:' . $term2->id() . ':0][term][depth]' => 1,
+    ];
+    // Because we can't post hidden form elements, we have to change them in
+    // code here, and then submit.
+    foreach ($hidden_edit as $field => $value) {
+      $node = $assert->hiddenFieldExists($field);
+      $node->setValue($value);
+    }
+    $edit = [
+      'terms[tid:' . $term2->id() . ':0][weight]' => 1,
+    ];
+    // Submit the edited form and check for HTML indentation element presence.
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->responseMatches('|<div class="js-indentation indentation">&nbsp;</div>|');
+
+    // Check explicitly that term 2's parent is term 1.
+    $parents = $taxonomy_storage->loadParents($term2->id());
+    $this->assertEquals(1, key($parents), 'Term 1 is the term 2\'s parent');
+
+    // Move the second term back out to the root level.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->get('vid') . '/overview');
+    $hidden_edit = [
+      'terms[tid:' . $term2->id() . ':0][term][tid]' => 2,
+      'terms[tid:' . $term2->id() . ':0][term][parent]' => 0,
+      'terms[tid:' . $term2->id() . ':0][term][depth]' => 0,
+    ];
+    // Because we can't post hidden form elements, we have to change them in
+    // code here, and then submit.
+    foreach ($hidden_edit as $field => $value) {
+      $node = $assert->hiddenFieldExists($field);
+      $node->setValue($value);
+    }
+    $edit = [
+      'terms[tid:' . $term2->id() . ':0][weight]' => 1,
+    ];
+    $this->submitForm($edit, 'Save');
+    // All terms back at the root level, no indentation should be present.
+    $this->assertSession()->responseNotMatches('|<div class="js-indentation indentation">&nbsp;</div>|');
+
+    // Check explicitly that term 2 has no parents.
+    \Drupal::entityTypeManager()->getStorage('taxonomy_term')->resetCache();
+    $parents = $taxonomy_storage->loadParents($term2->id());
+    $this->assertEmpty($parents, 'Term 2 has no parents now');
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TaxonomyTermPagerTest.php

@@ -0,0 +1,121 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+/**
+ * Ensures that the term pager works properly.
+ *
+ * @group taxonomy
+ */
+class TaxonomyTermPagerTest extends TaxonomyTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['taxonomy', 'taxonomy_test'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Vocabulary for testing.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer taxonomy',
+      'bypass node access',
+    ]));
+    $this->vocabulary = $this->createVocabulary();
+  }
+
+  /**
+   * Tests that the pager is displayed properly on the term overview page.
+   */
+  public function testTaxonomyTermOverviewPager(): void {
+    // Set limit to 3 terms per page.
+    $this->config('taxonomy.settings')
+      ->set('terms_per_page_admin', '3')
+      ->save();
+
+    // Create 3 terms.
+    for ($x = 1; $x <= 3; $x++) {
+      $this->createTerm($this->vocabulary);
+    }
+
+    // Get Page 1.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+    // Pager should not be visible.
+    $this->assertSession()->responseNotMatches('|<nav class="pager" [^>]*>|');
+
+    // Create 3 more terms to show pager.
+    for ($x = 1; $x <= 3; $x++) {
+      $this->createTerm($this->vocabulary);
+    }
+
+    // Ensure that pager is visible on page 1.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+    $this->assertSession()->responseMatches('|<nav class="pager" [^>]*>|');
+
+    // Ensure that pager is visible on page 2.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview', ['query' => ['page' => 1]]);
+    $this->assertSession()->responseMatches('|<nav class="pager" [^>]*>|');
+  }
+
+  /**
+   * Tests that overview page only loads the necessary terms.
+   */
+  public function testTaxonomyTermOverviewTermLoad(): void {
+    // Set limit to 3 terms per page.
+    $this->config('taxonomy.settings')
+      ->set('terms_per_page_admin', '3')
+      ->save();
+
+    $state = $this->container->get('state');
+
+    // Create 5 terms.
+    for ($x = 0; $x <= 10; $x++) {
+      $this->createTerm($this->vocabulary, ['weight' => $x]);
+    }
+
+    // Check the overview page.
+    $state->set('taxonomy_test_taxonomy_term_load', []);
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+    $loaded_terms = $state->get('taxonomy_test_taxonomy_term_load');
+    $this->assertCount(4, $loaded_terms);
+
+    // Check the overview page for submit callback.
+    $state->set('taxonomy_test_taxonomy_term_load', []);
+    $this->submitForm([], 'Save');
+    $loaded_terms = $state->get('taxonomy_test_taxonomy_term_load');
+    $this->assertCount(4, $loaded_terms);
+
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview', ['query' => ['page' => 2]]);
+    $state->set('taxonomy_test_taxonomy_term_load', []);
+    $this->submitForm([], 'Save');
+    $loaded_terms = $state->get('taxonomy_test_taxonomy_term_load');
+    $this->assertCount(4, $loaded_terms);
+
+    // Adding a new term with weight < 0 implies that all root terms are updated.
+    $this->createTerm($this->vocabulary, ['weight' => -1]);
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview', ['query' => ['page' => 2]]);
+    $state->set('taxonomy_test_taxonomy_term_load', []);
+    $this->submitForm([], 'Save');
+    $loaded_terms = $state->get('taxonomy_test_taxonomy_term_load');
+    $this->assertCount(12, $loaded_terms);
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TaxonomyTestBase.php

@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+use Drupal\Tests\field\Traits\EntityReferenceFieldCreationTrait;
+use Drupal\Tests\taxonomy\Traits\TaxonomyTestTrait;
+
+/**
+ * Provides common helper methods for Taxonomy module tests.
+ */
+abstract class TaxonomyTestBase extends BrowserTestBase {
+
+  use TaxonomyTestTrait;
+  use EntityReferenceFieldCreationTrait;
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['taxonomy', 'block'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->drupalPlaceBlock('system_breadcrumb_block');
+
+    // Create Basic page and Article node types.
+    if ($this->profile != 'standard') {
+      $this->drupalCreateContentType(['type' => 'article', 'name' => 'Article']);
+    }
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TaxonomyTranslationTestTrait.php

@@ -0,0 +1,102 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\language\Entity\ConfigurableLanguage;
+use Drupal\Tests\field\Traits\EntityReferenceFieldCreationTrait;
+
+/**
+ * Provides common testing base for translated taxonomy terms.
+ */
+trait TaxonomyTranslationTestTrait {
+
+  use EntityReferenceFieldCreationTrait;
+
+  /**
+   * The vocabulary.
+   *
+   * @var \Drupal\taxonomy\Entity\Vocabulary
+   */
+  protected $vocabulary;
+
+  /**
+   * The field name for our taxonomy term field.
+   *
+   * @var string
+   */
+  protected $termFieldName = 'field_tag';
+
+  /**
+   * The langcode of the source language.
+   *
+   * @var string
+   */
+  protected $baseLangcode = 'en';
+
+  /**
+   * Target langcode for translation.
+   *
+   * @var string
+   */
+  protected $translateToLangcode = 'hu';
+
+  /**
+   * The node to check the translated value on.
+   *
+   * @var \Drupal\node\Entity\Node
+   */
+  protected $node;
+
+  /**
+   * Adds additional languages.
+   */
+  protected function setupLanguages() {
+    ConfigurableLanguage::createFromLangcode($this->translateToLangcode)->save();
+    $this->rebuildContainer();
+  }
+
+  /**
+   * Enables translations where it needed.
+   */
+  protected function enableTranslation() {
+    // Enable translation for the current entity type and ensure the change is
+    // picked up.
+    \Drupal::service('content_translation.manager')->setEnabled('node', 'article', TRUE);
+    \Drupal::service('content_translation.manager')->setEnabled('taxonomy_term', $this->vocabulary->id(), TRUE);
+  }
+
+  /**
+   * Adds term reference field for the article content type.
+   */
+  protected function setUpTermReferenceField() {
+    $handler_settings = [
+      'target_bundles' => [
+        $this->vocabulary->id() => $this->vocabulary->id(),
+      ],
+      'auto_create' => TRUE,
+    ];
+    $this->createEntityReferenceField('node', 'article', $this->termFieldName, NULL, 'taxonomy_term', 'default', $handler_settings, FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED);
+    $field_storage = FieldStorageConfig::loadByName('node', $this->termFieldName);
+    $field_storage->setTranslatable(FALSE);
+    $field_storage->save();
+
+    /** @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface $display_repository */
+    $display_repository = \Drupal::service('entity_display.repository');
+
+    $display_repository->getFormDisplay('node', 'article')
+      ->setComponent($this->termFieldName, [
+        'type' => 'entity_reference_autocomplete_tags',
+      ])
+      ->save();
+    $display_repository->getViewDisplay('node', 'article')
+      ->setComponent($this->termFieldName, [
+        'type' => 'entity_reference_label',
+      ])
+      ->save();
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TermAccessTest.php

@@ -0,0 +1,133 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\taxonomy\Entity\Term;
+use Drupal\taxonomy\TermInterface;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
+
+/**
+ * Tests the taxonomy term access permissions.
+ *
+ * @group taxonomy
+ */
+class TermAccessTest extends TaxonomyTestBase {
+
+  use AssertPageCacheContextsAndTagsTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Tests access control functionality for taxonomy terms.
+   */
+  public function testTermAccess(): void {
+    $assert_session = $this->assertSession();
+
+    $vocabulary = $this->createVocabulary();
+
+    // Create two terms.
+    $published_term = Term::create([
+      'vid' => $vocabulary->id(),
+      'name' => 'Published term',
+      'status' => 1,
+    ]);
+    $published_term->save();
+    $unpublished_term = Term::create([
+      'vid' => $vocabulary->id(),
+      'name' => 'Unpublished term',
+      'status' => 0,
+    ]);
+    $unpublished_term->save();
+
+    // Start off logged in as admin.
+    $this->drupalLogin($this->drupalCreateUser(['administer taxonomy']));
+
+    // Test the 'administer taxonomy' permission.
+    $this->drupalGet('taxonomy/term/' . $published_term->id());
+    $assert_session->statusCodeEquals(200);
+    $this->assertTermAccess($published_term, 'view', TRUE);
+    $this->drupalGet('taxonomy/term/' . $unpublished_term->id());
+    $assert_session->statusCodeEquals(200);
+    $this->assertTermAccess($unpublished_term, 'view', TRUE);
+
+    $this->drupalGet('taxonomy/term/' . $published_term->id() . '/edit');
+    $assert_session->statusCodeEquals(200);
+    $this->assertTermAccess($published_term, 'update', TRUE);
+    $this->drupalGet('taxonomy/term/' . $unpublished_term->id() . '/edit');
+    $assert_session->statusCodeEquals(200);
+    $this->assertTermAccess($unpublished_term, 'update', TRUE);
+
+    $this->drupalGet('taxonomy/term/' . $published_term->id() . '/delete');
+    $assert_session->statusCodeEquals(200);
+    $this->assertTermAccess($published_term, 'delete', TRUE);
+    $this->drupalGet('taxonomy/term/' . $unpublished_term->id() . '/delete');
+    $assert_session->statusCodeEquals(200);
+    $this->assertTermAccess($unpublished_term, 'delete', TRUE);
+
+    // Test the 'access content' permission.
+    $this->drupalLogin($this->drupalCreateUser(['access content']));
+
+    $this->drupalGet('taxonomy/term/' . $published_term->id());
+    $assert_session->statusCodeEquals(200);
+    $this->assertTermAccess($published_term, 'view', TRUE);
+
+    $this->drupalGet('taxonomy/term/' . $unpublished_term->id());
+    $assert_session->statusCodeEquals(403);
+    $this->assertTermAccess($unpublished_term, 'view', FALSE, "The 'access content' permission is required and the taxonomy term must be published.");
+
+    $this->drupalGet('taxonomy/term/' . $published_term->id() . '/edit');
+    $assert_session->statusCodeEquals(403);
+    $this->assertTermAccess($published_term, 'update', FALSE, "The following permissions are required: 'edit terms in {$vocabulary->id()}' OR 'administer taxonomy'.");
+    $this->drupalGet('taxonomy/term/' . $unpublished_term->id() . '/edit');
+    $assert_session->statusCodeEquals(403);
+    $this->assertTermAccess($unpublished_term, 'update', FALSE, "The following permissions are required: 'edit terms in {$vocabulary->id()}' OR 'administer taxonomy'.");
+
+    $this->drupalGet('taxonomy/term/' . $published_term->id() . '/delete');
+    $assert_session->statusCodeEquals(403);
+    $this->assertTermAccess($published_term, 'delete', FALSE, "The following permissions are required: 'delete terms in {$vocabulary->id()}' OR 'administer taxonomy'.");
+    $this->drupalGet('taxonomy/term/' . $unpublished_term->id() . '/delete');
+    $assert_session->statusCodeEquals(403);
+    $this->assertTermAccess($unpublished_term, 'delete', FALSE, "The following permissions are required: 'delete terms in {$vocabulary->id()}' OR 'administer taxonomy'.");
+
+    // Install the Views module and repeat the checks for the 'view' permission.
+    \Drupal::service('module_installer')->install(['views'], TRUE);
+    $this->rebuildContainer();
+
+    $this->drupalGet('taxonomy/term/' . $published_term->id());
+    $assert_session->statusCodeEquals(200);
+
+    // @todo Change this assertion to expect a 403 status code when
+    //   https://www.drupal.org/project/drupal/issues/2983070 is fixed.
+    $this->drupalGet('taxonomy/term/' . $unpublished_term->id());
+    $assert_session->statusCodeEquals(404);
+  }
+
+  /**
+   * Checks access on taxonomy term.
+   *
+   * @param \Drupal\taxonomy\TermInterface $term
+   *   A taxonomy term entity.
+   * @param string $access_operation
+   *   The entity operation, e.g. 'view', 'edit', 'delete', etc.
+   * @param bool $access_allowed
+   *   Whether the current use has access to the given operation or not.
+   * @param string $access_reason
+   *   (optional) The reason of the access result.
+   *
+   * @internal
+   */
+  protected function assertTermAccess(TermInterface $term, string $access_operation, bool $access_allowed, string $access_reason = ''): void {
+    $access_result = $term->access($access_operation, NULL, TRUE);
+    $this->assertSame($access_allowed, $access_result->isAllowed());
+
+    if ($access_reason) {
+      $this->assertSame($access_reason, $access_result->getReason());
+    }
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TermAutocompleteTest.php

@@ -0,0 +1,236 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Component\Serialization\Json;
+use Drupal\Core\Entity\Entity\EntityFormDisplay;
+use Drupal\Core\Entity\Entity\EntityViewDisplay;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\field\Entity\FieldConfig;
+use Drupal\field\Entity\FieldStorageConfig;
+
+/**
+ * Tests the autocomplete implementation of the taxonomy class.
+ *
+ * @group taxonomy
+ */
+class TermAutocompleteTest extends TaxonomyTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['node'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * The vocabulary.
+   *
+   * @var \Drupal\taxonomy\Entity\Vocabulary
+   */
+  protected $vocabulary;
+
+  /**
+   * The field to add to the content type for the taxonomy terms.
+   *
+   * @var string
+   */
+  protected $fieldName;
+
+  /**
+   * The admin user.
+   *
+   * @var \Drupal\user\Entity\User
+   */
+  protected $adminUser;
+
+  /**
+   * The autocomplete URL to call.
+   *
+   * @var string
+   */
+  protected $autocompleteUrl;
+
+  /**
+   * The term IDs indexed by term names.
+   *
+   * @var array
+   */
+  protected $termIds;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    // Create a vocabulary.
+    $this->vocabulary = $this->createVocabulary();
+
+    // Create 11 terms, which have some sub-string in common, in a
+    // non-alphabetical order, so that we will have more than 10 matches later
+    // when we test the correct number of results is returned, and we can test
+    // the order of the results. The location of the sub-string to match varies
+    // also, since it should not be necessary to start with the sub-string to
+    // match it. Save term IDs to reuse later.
+    $termNames = [
+      'aaa 20 bbb',
+      'aaa 70 bbb',
+      'aaa 10 bbb',
+      'aaa 12 bbb',
+      'aaa 40 bbb',
+      'aaa 11 bbb',
+      'aaa 30 bbb',
+      'aaa 50 bbb',
+      'aaa 80',
+      'aaa 90',
+      'bbb 60 aaa',
+    ];
+    foreach ($termNames as $termName) {
+      $term = $this->createTerm($this->vocabulary, ['name' => $termName]);
+      $this->termIds[$termName] = $term->id();
+    }
+
+    // Create a taxonomy_term_reference field on the article Content Type that
+    // uses a taxonomy_autocomplete widget.
+    $this->fieldName = $this->randomMachineName();
+    FieldStorageConfig::create([
+      'field_name' => $this->fieldName,
+      'entity_type' => 'node',
+      'type' => 'entity_reference',
+      'cardinality' => FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED,
+      'settings' => [
+        'target_type' => 'taxonomy_term',
+      ],
+    ])->save();
+    FieldConfig::create([
+      'field_name' => $this->fieldName,
+      'bundle' => 'article',
+      'entity_type' => 'node',
+      'settings' => [
+        'handler' => 'default',
+        'handler_settings' => [
+          // Restrict selection of terms to a single vocabulary.
+          'target_bundles' => [
+            $this->vocabulary->id() => $this->vocabulary->id(),
+          ],
+        ],
+      ],
+    ])->save();
+    EntityFormDisplay::load('node.article.default')
+      ->setComponent($this->fieldName, [
+        'type' => 'entity_reference_autocomplete',
+      ])
+      ->save();
+    EntityViewDisplay::load('node.article.default')
+      ->setComponent($this->fieldName, [
+        'type' => 'entity_reference_label',
+      ])
+      ->save();
+
+    // Create a user and then login.
+    $this->adminUser = $this->drupalCreateUser(['create article content']);
+    $this->drupalLogin($this->adminUser);
+
+    // Retrieve the autocomplete URL.
+    $this->drupalGet('node/add/article');
+    $field = $this->assertSession()->fieldExists("{$this->fieldName}[0][target_id]");
+    $this->autocompleteUrl = $this->getAbsoluteUrl($field->getAttribute('data-autocomplete-path'));
+  }
+
+  /**
+   * Helper function for JSON formatted requests.
+   *
+   * @param string|\Drupal\Core\Url $path
+   *   Drupal path or URL to load into Mink controlled browser.
+   * @param array $options
+   *   (optional) Options to be forwarded to the URL generator.
+   * @param string[] $headers
+   *   (optional) An array containing additional HTTP request headers.
+   *
+   * @return string[]
+   *   Array representing decoded JSON response.
+   */
+  protected function drupalGetJson($path, array $options = [], array $headers = []) {
+    $options = array_merge_recursive(['query' => ['_format' => 'json']], $options);
+    return Json::decode($this->drupalGet($path, $options, $headers));
+  }
+
+  /**
+   * Tests that the autocomplete method returns the good number of results.
+   *
+   * @see \Drupal\taxonomy\Controller\TermAutocompleteController::autocomplete()
+   */
+  public function testAutocompleteCountResults(): void {
+    // Test that no matching term found.
+    $data = $this->drupalGetJson(
+      $this->autocompleteUrl,
+      ['query' => ['q' => 'zzz']]
+    );
+    $this->assertEmpty($data, 'Autocomplete returned no results');
+
+    // Test that only one matching term found, when only one matches.
+    $data = $this->drupalGetJson(
+      $this->autocompleteUrl,
+      ['query' => ['q' => 'aaa 10']]
+    );
+    $this->assertCount(1, $data, 'Autocomplete returned 1 result');
+
+    // Test the correct number of matches when multiple are partial matches.
+    $data = $this->drupalGetJson(
+      $this->autocompleteUrl,
+      ['query' => ['q' => 'aaa 1']]
+    );
+    $this->assertCount(3, $data, 'Autocomplete returned 3 results');
+
+    // Tests that only 10 results are returned, even if there are more than 10
+    // matches.
+    $data = $this->drupalGetJson(
+      $this->autocompleteUrl,
+      ['query' => ['q' => 'aaa']]
+    );
+    $this->assertCount(10, $data, 'Autocomplete returned only 10 results (for over 10 matches)');
+  }
+
+  /**
+   * Tests that the autocomplete method returns properly ordered results.
+   *
+   * @see \Drupal\taxonomy\Controller\TermAutocompleteController::autocomplete()
+   */
+  public function testAutocompleteOrderedResults(): void {
+    $expectedResults = [
+      'aaa 10 bbb',
+      'aaa 11 bbb',
+      'aaa 12 bbb',
+      'aaa 20 bbb',
+      'aaa 30 bbb',
+      'aaa 40 bbb',
+      'aaa 50 bbb',
+      'aaa 70 bbb',
+      'bbb 60 aaa',
+    ];
+    // Build $expected to match the autocomplete results.
+    $expected = [];
+    foreach ($expectedResults as $termName) {
+      $expected[] = [
+        'value' => $termName . ' (' . $this->termIds[$termName] . ')',
+        'label' => $termName,
+      ];
+    }
+
+    $data = $this->drupalGetJson(
+      $this->autocompleteUrl,
+      ['query' => ['q' => 'bbb']]
+    );
+
+    $this->assertSame($expected, $data);
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TermCacheTagsTest.php

@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\taxonomy\Entity\Vocabulary;
+use Drupal\taxonomy\Entity\Term;
+use Drupal\Tests\system\Functional\Entity\EntityWithUriCacheTagsTestBase;
+
+/**
+ * Tests the Taxonomy term entity's cache tags.
+ *
+ * @group taxonomy
+ */
+class TermCacheTagsTest extends EntityWithUriCacheTagsTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['taxonomy'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function createEntity() {
+    // Create a "Camelids" vocabulary.
+    $vocabulary = Vocabulary::create([
+      'name' => 'Camelids',
+      'vid' => 'camelids',
+    ]);
+    $vocabulary->save();
+
+    // Create a "Llama" taxonomy term.
+    $term = Term::create([
+      'name' => 'Llama',
+      'vid' => $vocabulary->id(),
+    ]);
+    $term->save();
+
+    return $term;
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TermContextualLinksTest.php

@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+/**
+ * Tests views contextual links on terms.
+ *
+ * @group taxonomy
+ */
+class TermContextualLinksTest extends TaxonomyTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'contextual',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Tests contextual links.
+   */
+  public function testTermContextualLinks(): void {
+    $vocabulary = $this->createVocabulary();
+    $term = $this->createTerm($vocabulary);
+
+    $user = $this->drupalCreateUser([
+      'administer taxonomy',
+      'access contextual links',
+    ]);
+    $this->drupalLogin($user);
+
+    $this->drupalGet('taxonomy/term/' . $term->id());
+    $this->assertSession()->elementExists('css', 'div[data-contextual-id^="taxonomy_term:taxonomy_term=' . $term->id() . ':"]');
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TermIndexTest.php

@@ -0,0 +1,259 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Core\Link;
+use Drupal\Core\Database\Database;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+
+/**
+ * Tests the hook implementations that maintain the taxonomy index.
+ *
+ * @group taxonomy
+ */
+class TermIndexTest extends TaxonomyTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['views'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Vocabulary for testing.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  /**
+   * Name of the taxonomy term reference field.
+   *
+   * @var string
+   */
+  protected $fieldName1;
+
+  /**
+   * Name of the taxonomy term reference field.
+   *
+   * @var string
+   */
+  protected $fieldName2;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    // Create an administrative user.
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer taxonomy',
+      'bypass node access',
+    ]));
+
+    // Create a vocabulary and add two term reference fields to article nodes.
+    $this->vocabulary = $this->createVocabulary();
+
+    $this->fieldName1 = $this->randomMachineName();
+    $handler_settings = [
+      'target_bundles' => [
+        $this->vocabulary->id() => $this->vocabulary->id(),
+      ],
+      'auto_create' => TRUE,
+    ];
+    $this->createEntityReferenceField('node', 'article', $this->fieldName1, NULL, 'taxonomy_term', 'default', $handler_settings, FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED);
+
+    /** @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface $display_repository */
+    $display_repository = \Drupal::service('entity_display.repository');
+    $display_repository->getFormDisplay('node', 'article')
+      ->setComponent($this->fieldName1, [
+        'type' => 'options_select',
+      ])
+      ->save();
+    $display_repository->getViewDisplay('node', 'article')
+      ->setComponent($this->fieldName1, [
+        'type' => 'entity_reference_label',
+      ])
+      ->save();
+
+    $this->fieldName2 = $this->randomMachineName();
+    $this->createEntityReferenceField('node', 'article', $this->fieldName2, NULL, 'taxonomy_term', 'default', $handler_settings, FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED);
+
+    /** @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface $display_repository */
+    $display_repository = \Drupal::service('entity_display.repository');
+    $display_repository->getFormDisplay('node', 'article')
+      ->setComponent($this->fieldName2, [
+        'type' => 'options_select',
+      ])
+      ->save();
+    $display_repository->getViewDisplay('node', 'article')
+      ->setComponent($this->fieldName2, [
+        'type' => 'entity_reference_label',
+      ])
+      ->save();
+  }
+
+  /**
+   * Tests that the taxonomy index is maintained properly.
+   */
+  public function testTaxonomyIndex(): void {
+    $node_storage = $this->container->get('entity_type.manager')->getStorage('node');
+    // Create terms in the vocabulary.
+    $term_1 = $this->createTerm($this->vocabulary);
+    $term_2 = $this->createTerm($this->vocabulary);
+
+    // Post an article.
+    $edit = [];
+    $edit['title[0][value]'] = $this->randomMachineName();
+    $edit['body[0][value]'] = $this->randomMachineName();
+    $edit["{$this->fieldName1}[]"] = $term_1->id();
+    $edit["{$this->fieldName2}[]"] = $term_1->id();
+    $this->drupalGet('node/add/article');
+    $this->submitForm($edit, 'Save');
+
+    // Check that the term is indexed, and only once.
+    $node = $this->drupalGetNodeByTitle($edit['title[0][value]']);
+    $connection = Database::getConnection();
+    $index_count = $connection->select('taxonomy_index')
+      ->condition('nid', $node->id())
+      ->condition('tid', $term_1->id())
+      ->countQuery()
+      ->execute()
+      ->fetchField();
+    $this->assertEquals(1, $index_count, 'Term 1 is indexed once.');
+
+    // Update the article to change one term.
+    $edit["{$this->fieldName1}[]"] = $term_2->id();
+    $this->drupalGet('node/' . $node->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+
+    // Check that both terms are indexed.
+    $index_count = $connection->select('taxonomy_index')
+      ->condition('nid', $node->id())
+      ->condition('tid', $term_1->id())
+      ->countQuery()
+      ->execute()
+      ->fetchField();
+    $this->assertEquals(1, $index_count, 'Term 1 is indexed.');
+    $index_count = $connection->select('taxonomy_index')
+      ->condition('nid', $node->id())
+      ->condition('tid', $term_2->id())
+      ->countQuery()
+      ->execute()
+      ->fetchField();
+    $this->assertEquals(1, $index_count, 'Term 2 is indexed.');
+
+    // Update the article to change another term.
+    $edit["{$this->fieldName2}[]"] = $term_2->id();
+    $this->drupalGet('node/' . $node->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+
+    // Check that only one term is indexed.
+    $index_count = $connection->select('taxonomy_index')
+      ->condition('nid', $node->id())
+      ->condition('tid', $term_1->id())
+      ->countQuery()
+      ->execute()
+      ->fetchField();
+    $this->assertEquals(0, $index_count, 'Term 1 is not indexed.');
+    $index_count = $connection->select('taxonomy_index')
+      ->condition('nid', $node->id())
+      ->condition('tid', $term_2->id())
+      ->countQuery()
+      ->execute()
+      ->fetchField();
+    $this->assertEquals(1, $index_count, 'Term 2 is indexed once.');
+
+    // Redo the above tests without interface.
+    $node_storage->resetCache([$node->id()]);
+    $node = $node_storage->load($node->id());
+    $node->title = $this->randomMachineName();
+
+    // Update the article with no term changed.
+    $node->save();
+
+    // Check that the index was not changed.
+    $index_count = $connection->select('taxonomy_index')
+      ->condition('nid', $node->id())
+      ->condition('tid', $term_1->id())
+      ->countQuery()
+      ->execute()
+      ->fetchField();
+    $this->assertEquals(0, $index_count, 'Term 1 is not indexed.');
+    $index_count = $connection->select('taxonomy_index')
+      ->condition('nid', $node->id())
+      ->condition('tid', $term_2->id())
+      ->countQuery()
+      ->execute()
+      ->fetchField();
+    $this->assertEquals(1, $index_count, 'Term 2 is indexed once.');
+
+    // Update the article to change one term.
+    $node->{$this->fieldName1} = [['target_id' => $term_1->id()]];
+    $node->save();
+
+    // Check that both terms are indexed.
+    $index_count = $connection->select('taxonomy_index')
+      ->condition('nid', $node->id())
+      ->condition('tid', $term_1->id())
+      ->countQuery()
+      ->execute()
+      ->fetchField();
+    $this->assertEquals(1, $index_count, 'Term 1 is indexed.');
+    $index_count = $connection->select('taxonomy_index')
+      ->condition('nid', $node->id())
+      ->condition('tid', $term_2->id())
+      ->countQuery()
+      ->execute()
+      ->fetchField();
+    $this->assertEquals(1, $index_count, 'Term 2 is indexed.');
+
+    // Update the article to change another term.
+    $node->{$this->fieldName2} = [['target_id' => $term_1->id()]];
+    $node->save();
+
+    // Check that only one term is indexed.
+    $index_count = $connection->select('taxonomy_index')
+      ->condition('nid', $node->id())
+      ->condition('tid', $term_1->id())
+      ->countQuery()
+      ->execute()
+      ->fetchField();
+    $this->assertEquals(1, $index_count, 'Term 1 is indexed once.');
+    $index_count = $connection->select('taxonomy_index')
+      ->condition('nid', $node->id())
+      ->condition('tid', $term_2->id())
+      ->countQuery()
+      ->execute()
+      ->fetchField();
+    $this->assertEquals(0, $index_count, 'Term 2 is not indexed.');
+  }
+
+  /**
+   * Tests that there is a link to the parent term on the child term page.
+   */
+  public function testTaxonomyTermHierarchyBreadcrumbs(): void {
+    // Create two taxonomy terms and set term2 as the parent of term1.
+    $term1 = $this->createTerm($this->vocabulary);
+    $term2 = $this->createTerm($this->vocabulary);
+    $term1->parent = [$term2->id()];
+    $term1->save();
+
+    // Verify that the page breadcrumbs include a link to the parent term.
+    $this->drupalGet('taxonomy/term/' . $term1->id());
+    // Breadcrumbs are not rendered with a language, prevent the term
+    // language from being added to the options.
+    // Check that parent term link is displayed when viewing the node.
+    $this->assertSession()->responseContains(Link::fromTextAndUrl($term2->getName(), $term2->toUrl('canonical', ['language' => NULL]))->toString());
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TermLanguageTest.php

@@ -0,0 +1,163 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Core\Language\LanguageInterface;
+use Drupal\language\Entity\ConfigurableLanguage;
+
+/**
+ * Tests the language functionality for the taxonomy terms.
+ *
+ * @group taxonomy
+ */
+class TermLanguageTest extends TaxonomyTestBase {
+
+  protected static $modules = ['language'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Vocabulary for testing.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    // Create an administrative user.
+    $this->drupalLogin($this->drupalCreateUser(['administer taxonomy']));
+
+    // Create a vocabulary to which the terms will be assigned.
+    $this->vocabulary = $this->createVocabulary();
+
+    // Add some custom languages.
+    foreach (['aa', 'bb', 'cc'] as $language_code) {
+      ConfigurableLanguage::create([
+        'id' => $language_code,
+        'label' => $this->randomMachineName(),
+      ])->save();
+    }
+  }
+
+  public function testTermLanguage(): void {
+    // Configure the vocabulary to not hide the language selector.
+    $edit = [
+      'default_language[language_alterable]' => TRUE,
+    ];
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id());
+    $this->submitForm($edit, 'Save');
+
+    // Add a term.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    // Check that we have the language selector.
+    $this->assertSession()->fieldExists('edit-langcode-0-value');
+    // Submit the term.
+    $edit = [
+      'name[0][value]' => $this->randomMachineName(),
+      'langcode[0][value]' => 'aa',
+    ];
+    $this->submitForm($edit, 'Save');
+    $terms = \Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadByProperties([
+      'name' => $edit['name[0][value]'],
+    ]);
+    $term = reset($terms);
+    $this->assertEquals($edit['langcode[0][value]'], $term->language()->getId(), 'The term contains the correct langcode.');
+
+    // Check if on the edit page the language is correct.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $this->assertTrue($this->assertSession()->optionExists('edit-langcode-0-value', $edit['langcode[0][value]'])->isSelected());
+
+    // Change the language of the term.
+    $edit['langcode[0][value]'] = 'bb';
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+
+    // Check again that on the edit page the language is correct.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $this->assertTrue($this->assertSession()->optionExists('edit-langcode-0-value', $edit['langcode[0][value]'])->isSelected());
+  }
+
+  public function testDefaultTermLanguage(): void {
+    // Configure the vocabulary to not hide the language selector, and make the
+    // default language of the terms fixed.
+    $edit = [
+      'default_language[langcode]' => 'bb',
+      'default_language[language_alterable]' => TRUE,
+    ];
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id());
+    $this->submitForm($edit, 'Save');
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    $this->assertTrue($this->assertSession()->optionExists('edit-langcode-0-value', 'bb')->isSelected());
+
+    // Make the default language of the terms to be the current interface.
+    $edit = [
+      'default_language[langcode]' => 'current_interface',
+      'default_language[language_alterable]' => TRUE,
+    ];
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id());
+    $this->submitForm($edit, 'Save');
+    $this->drupalGet('aa/admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    $this->assertTrue($this->assertSession()->optionExists('edit-langcode-0-value', 'aa')->isSelected());
+    $this->drupalGet('bb/admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    $this->assertTrue($this->assertSession()->optionExists('edit-langcode-0-value', 'bb')->isSelected());
+
+    // Change the default language of the site and check if the default terms
+    // language is still correctly selected.
+    $this->config('system.site')->set('default_langcode', 'cc')->save();
+    $edit = [
+      'default_language[langcode]' => LanguageInterface::LANGCODE_SITE_DEFAULT,
+      'default_language[language_alterable]' => TRUE,
+    ];
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id());
+    $this->submitForm($edit, 'Save');
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    $this->assertTrue($this->assertSession()->optionExists('edit-langcode-0-value', 'cc')->isSelected());
+  }
+
+  /**
+   * Tests that translated terms are displayed correctly on the term overview.
+   */
+  public function testTermTranslatedOnOverviewPage(): void {
+    // Configure the vocabulary to not hide the language selector.
+    $edit = [
+      'default_language[language_alterable]' => TRUE,
+    ];
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id());
+    $this->submitForm($edit, 'Save');
+
+    // Add a term.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    // Submit the term.
+    $edit = [
+      'name[0][value]' => $this->randomMachineName(),
+      'langcode[0][value]' => 'aa',
+    ];
+    $this->submitForm($edit, 'Save');
+    $terms = \Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadByProperties([
+      'name' => $edit['name[0][value]'],
+    ]);
+    $term = reset($terms);
+
+    // Add a translation for that term.
+    $translated_title = $this->randomMachineName();
+    $term->addTranslation('bb', [
+      'name' => $translated_title,
+    ]);
+    $term->save();
+
+    // Overview page in the other language shows the translated term
+    $this->drupalGet('bb/admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+    $this->assertSession()->responseMatches('|<a[^>]*>' . $translated_title . '</a>|');
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TermParentsTest.php

@@ -0,0 +1,363 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\taxonomy\Entity\Vocabulary;
+use Drupal\taxonomy\TermInterface;
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Tests managing taxonomy parents through the user interface.
+ *
+ * @group taxonomy
+ */
+class TermParentsTest extends BrowserTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['taxonomy_test'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * The term storage.
+   *
+   * @var \Drupal\taxonomy\TermStorageInterface
+   */
+  protected $termStorage;
+
+  /**
+   * The state service.
+   *
+   * @var \Drupal\Core\State\StateInterface
+   */
+  protected $state;
+
+  /**
+   * The ID of the vocabulary used in this test.
+   *
+   * @var string
+   */
+  protected $vocabularyId = 'test_vocabulary';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    /** @var \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager */
+    $entity_type_manager = $this->container->get('entity_type.manager');
+    $this->termStorage = $entity_type_manager->getStorage('taxonomy_term');
+    $this->state = $this->container->get('state');
+
+    Vocabulary::create(['vid' => $this->vocabularyId, 'name' => 'Test'])->save();
+    $this->drupalLogin($this->drupalCreateUser(['administer taxonomy']));
+  }
+
+  /**
+   * Tests specifying parents when creating terms.
+   */
+  public function testAddWithParents(): void {
+    $this->drupalGet("/admin/structure/taxonomy/manage/{$this->vocabularyId}/add");
+    $page = $this->getSession()->getPage();
+
+    // Create a term without any parents.
+    $term_1 = $this->submitAddTermForm('Test term 1');
+    $expected = [['target_id' => 0]];
+    $this->assertEquals($expected, $term_1->get('parent')->getValue());
+
+    // Explicitly selecting <root> should have the same effect as not selecting
+    // anything.
+    $page->selectFieldOption('Parent terms', '<root>');
+    $term_2 = $this->submitAddTermForm('Test term 2');
+    $this->assertEquals($expected, $term_2->get('parent')->getValue());
+
+    // Create two terms with the previously created ones as parents,
+    // respectively.
+    $page->selectFieldOption('Parent terms', 'Test term 1');
+    $term_3 = $this->submitAddTermForm('Test term 3');
+    $expected = [['target_id' => $term_1->id()]];
+    $this->assertEquals($expected, $term_3->get('parent')->getValue());
+    $page->selectFieldOption('Parent terms', 'Test term 2');
+    $term_4 = $this->submitAddTermForm('Test term 4');
+    $expected = [['target_id' => $term_2->id()]];
+    $this->assertEquals($expected, $term_4->get('parent')->getValue());
+
+    // Create a term with term 3 as parent.
+    $page->selectFieldOption('Parent terms', '-Test term 3');
+    $term_5 = $this->submitAddTermForm('Test term 5');
+    $expected = [['target_id' => $term_3->id()]];
+    $this->assertEquals($expected, $term_5->get('parent')->getValue());
+
+    // Create a term with multiple parents.
+    $page->selectFieldOption('Parent terms', '--Test term 5');
+    $page->selectFieldOption('Parent terms', '-Test term 4', TRUE);
+    $term_6 = $this->submitAddTermForm('Test term 6');
+    $expected = [
+      ['target_id' => $term_5->id()],
+      ['target_id' => $term_4->id()],
+    ];
+    $this->assertEquals($expected, $term_6->get('parent')->getValue());
+  }
+
+  /**
+   * Creates a term through the user interface and returns it.
+   *
+   * @param string $name
+   *   The name of the term to create.
+   *
+   * @return \Drupal\taxonomy\TermInterface
+   *   The newly created taxonomy term.
+   */
+  protected function submitAddTermForm($name) {
+    $this->getSession()->getPage()->fillField('Name', $name);
+
+    $this->submitForm([], 'Save');
+
+    $result = $this->termStorage
+      ->getQuery()
+      ->accessCheck(FALSE)
+      ->condition('name', $name)
+      ->execute();
+    /** @var \Drupal\taxonomy\TermInterface $term_1 */
+    $term_1 = $this->termStorage->load(reset($result));
+    $this->assertInstanceOf(TermInterface::class, $term_1);
+    return $term_1;
+  }
+
+  /**
+   * Tests editing the parents of existing terms.
+   */
+  public function testEditingParents(): void {
+    $terms = $this->doTestEditingSingleParent();
+    $term_5 = array_pop($terms);
+    $term_4 = array_pop($terms);
+
+    // Create a term with multiple parents.
+    $term_6 = $this->createTerm('Test term 6', [
+      // Term 5 comes before term 4 in the user interface, so add the parents in
+      // the matching order.
+      $term_5->id(),
+      $term_4->id(),
+    ]);
+    $this->drupalGet($term_6->toUrl('edit-form'));
+    $this->assertParentOption('<root>');
+    $this->assertParentOption('Test term 1');
+    $this->assertParentOption('-Test term 3');
+    $this->assertParentOption('--Test term 5', TRUE);
+    $this->assertParentOption('Test term 2');
+    $this->assertParentOption('-Test term 4', TRUE);
+    $this->submitForm([], 'Save');
+    $this->assertParentsUnchanged($term_6);
+  }
+
+  /**
+   * Tests specifying parents when creating terms and a disabled parent form.
+   */
+  public function testEditingParentsWithDisabledFormElement(): void {
+    // Disable the parent form element.
+    $this->state->set('taxonomy_test.disable_parent_form_element', TRUE);
+    $this->drupalGet("/admin/structure/taxonomy/manage/{$this->vocabularyId}/add");
+    $this->assertSession()->fieldDisabled('Parent terms');
+
+    $terms = $this->doTestEditingSingleParent();
+    $term_5 = array_pop($terms);
+    $term_4 = array_pop($terms);
+
+    // Create a term with multiple parents.
+    $term_6 = $this->createTerm('Test term 6', [
+      // When the parent form element is disabled, its default value is used as
+      // the value which gets populated in ascending order of term IDs.
+      $term_4->id(),
+      $term_5->id(),
+    ]);
+    $this->drupalGet($term_6->toUrl('edit-form'));
+    $this->assertParentOption('<root>');
+    $this->assertParentOption('Test term 1');
+    $this->assertParentOption('-Test term 3');
+    $this->assertParentOption('--Test term 5', TRUE);
+    $this->assertParentOption('Test term 2');
+    $this->assertParentOption('-Test term 4', TRUE);
+    $this->submitForm([], 'Save');
+    $this->assertParentsUnchanged($term_6);
+  }
+
+  /**
+   * Performs tests that edit terms with a single parent.
+   *
+   * @return \Drupal\taxonomy\TermInterface[]
+   *   A list of terms created for testing.
+   */
+  protected function doTestEditingSingleParent() {
+    $terms = [];
+
+    // Create two terms without any parents.
+    $term_1 = $this->createTerm('Test term 1');
+    $this->drupalGet($term_1->toUrl('edit-form'));
+    $this->assertParentOption('<root>', TRUE);
+    $this->submitForm([], 'Save');
+    $this->assertParentsUnchanged($term_1);
+    $terms[] = $term_1;
+
+    $term_2 = $this->createTerm('Test term 2');
+    $this->drupalGet($term_2->toUrl('edit-form'));
+    $this->assertParentOption('<root>', TRUE);
+    $this->assertParentOption('Test term 1');
+    $this->submitForm([], 'Save');
+    $this->assertParentsUnchanged($term_2);
+    $terms[] = $term_2;
+
+    // Create two terms with the previously created terms as parents,
+    // respectively.
+    $term_3 = $this->createTerm('Test term 3', [$term_1->id()]);
+    $this->drupalGet($term_3->toUrl('edit-form'));
+    $this->assertParentOption('<root>');
+    $this->assertParentOption('Test term 1', TRUE);
+    $this->assertParentOption('Test term 2');
+    $this->submitForm([], 'Save');
+    $this->assertParentsUnchanged($term_3);
+    $terms[] = $term_3;
+
+    $term_4 = $this->createTerm('Test term 4', [$term_2->id()]);
+    $this->drupalGet($term_4->toUrl('edit-form'));
+    $this->assertParentOption('<root>');
+    $this->assertParentOption('Test term 1');
+    $this->assertParentOption('-Test term 3');
+    $this->assertParentOption('Test term 2', TRUE);
+    $this->submitForm([], 'Save');
+    $this->assertParentsUnchanged($term_4);
+    $terms[] = $term_4;
+
+    // Create a term with term 3 as parent.
+    $term_5 = $this->createTerm('Test term 5', [$term_3->id()]);
+    $this->drupalGet($term_5->toUrl('edit-form'));
+    $this->assertParentOption('<root>');
+    $this->assertParentOption('Test term 1');
+    $this->assertParentOption('-Test term 3', TRUE);
+    $this->assertParentOption('Test term 2');
+    $this->assertParentOption('-Test term 4');
+    $this->submitForm([], 'Save');
+    $this->assertParentsUnchanged($term_5);
+    $terms[] = $term_5;
+
+    return $terms;
+  }
+
+  /**
+   * Test the term add/edit form with parent query parameter.
+   */
+  public function testParentFromQuery(): void {
+    // Create three terms without any parents.
+    $term_1 = $this->createTerm('Test term 1');
+    $term_2 = $this->createTerm('Test term 2');
+    $term_3 = $this->createTerm('Test term 3');
+
+    // Add term form with one parent.
+    $this->drupalGet("/admin/structure/taxonomy/manage/{$this->vocabularyId}/add", ['query' => ['parent' => $term_1->id()]]);
+    $this->assertParentOption('Test term 1', TRUE);
+    $this->assertParentOption('Test term 2', FALSE);
+    $this->assertParentOption('Test term 3', FALSE);
+    // Add term form with two parents.
+    $this->drupalGet("/admin/structure/taxonomy/manage/{$this->vocabularyId}/add", ['query' => ['parent[0]' => $term_1->id(), 'parent[1]' => $term_2->id()]]);
+    $this->assertParentOption('Test term 1', TRUE);
+    $this->assertParentOption('Test term 2', TRUE);
+    $this->assertParentOption('Test term 3', FALSE);
+    // Add term form with no parents.
+    $this->drupalGet("/admin/structure/taxonomy/manage/{$this->vocabularyId}/add", ['query' => ['parent' => '']]);
+    $this->assertParentOption('Test term 1', FALSE);
+    $this->assertParentOption('Test term 2', FALSE);
+    $this->assertParentOption('Test term 3', FALSE);
+    // Add term form with invalid parent.
+    $this->drupalGet("/admin/structure/taxonomy/manage/{$this->vocabularyId}/add", ['query' => ['parent' => -1]]);
+    $this->assertParentOption('Test term 1', FALSE);
+    $this->assertParentOption('Test term 2', FALSE);
+    $this->assertParentOption('Test term 3', FALSE);
+
+    // Edit term form with one parent.
+    $this->drupalGet($term_1->toUrl('edit-form'), ['query' => ['parent' => $term_2->id()]]);
+    $this->assertParentOption('Test term 2', TRUE);
+    $this->assertParentOption('Test term 3', FALSE);
+    // Edit term form with two parents.
+    $this->drupalGet($term_1->toUrl('edit-form'), ['query' => ['parent[0]' => $term_2->id(), 'parent[1]' => $term_3->id()]]);
+    $this->assertParentOption('Test term 2', TRUE);
+    $this->assertParentOption('Test term 3', TRUE);
+    // Edit term form with no parents.
+    $this->drupalGet($term_1->toUrl('edit-form'), ['query' => ['parent' => '']]);
+    $this->assertParentOption('Test term 2', FALSE);
+    $this->assertParentOption('Test term 3', FALSE);
+    // Edit term form with invalid parent.
+    $this->drupalGet($term_1->toUrl('edit-form'), ['query' => ['parent' => -1]]);
+    $this->assertParentOption('Test term 2', FALSE);
+    $this->assertParentOption('Test term 3', FALSE);
+  }
+
+  /**
+   * Creates a term, saves it and returns it.
+   *
+   * @param string $name
+   *   The name of the term to create
+   * @param int[] $parent_ids
+   *   (optional) A list of parent term IDs.
+   *
+   * @return \Drupal\taxonomy\TermInterface
+   *   The created term.
+   */
+  protected function createTerm($name, array $parent_ids = []) {
+    /** @var \Drupal\taxonomy\TermInterface $term */
+    $term = $this->termStorage->create([
+      'name' => $name,
+      'vid' => $this->vocabularyId,
+    ]);
+    foreach ($parent_ids as $delta => $parent_id) {
+      $term->get('parent')->set($delta, ['target_id' => $parent_id]);
+    }
+
+    $term->save();
+
+    return $term;
+  }
+
+  /**
+   * Asserts that an option in the parent form element of terms exists.
+   *
+   * @param string $option
+   *   The label of the parent option.
+   * @param bool $selected
+   *   (optional) Whether or not the option should be selected. Defaults to
+   *   FALSE.
+   *
+   * @internal
+   */
+  protected function assertParentOption(string $option, bool $selected = FALSE): void {
+    $option = $this->assertSession()->optionExists('Parent terms', $option);
+    if ($selected) {
+      $this->assertTrue($option->hasAttribute('selected'));
+    }
+    else {
+      $this->assertFalse($option->hasAttribute('selected'));
+    }
+  }
+
+  /**
+   * Asserts that the parents of the term have not changed after saving.
+   *
+   * @param \Drupal\taxonomy\TermInterface $term
+   *   The term to check.
+   *
+   * @internal
+   */
+  protected function assertParentsUnchanged(TermInterface $term): void {
+    $saved_term = $this->termStorage->load($term->id());
+
+    $expected = $term->get('parent')->getValue();
+    $this->assertEquals($expected, $saved_term->get('parent')->getValue());
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TermTest.php

@@ -0,0 +1,685 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Component\Utility\Tags;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\field\Entity\FieldConfig;
+use Drupal\taxonomy\Entity\Term;
+use Drupal\taxonomy\TermInterface;
+use Drupal\Tests\system\Functional\Menu\AssertBreadcrumbTrait;
+
+/**
+ * Tests load, save and delete for taxonomy terms.
+ *
+ * @group taxonomy
+ * @group #slow
+ */
+class TermTest extends TaxonomyTestBase {
+
+  use AssertBreadcrumbTrait;
+
+  /**
+   * Vocabulary for testing.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  /**
+   * Taxonomy term reference field for testing.
+   *
+   * @var \Drupal\field\FieldConfigInterface
+   */
+  protected $field;
+
+  /**
+   * Modules to enable.
+   *
+   * @var string[]
+   */
+  protected static $modules = ['block'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->drupalPlaceBlock('local_actions_block');
+    $this->drupalPlaceBlock('local_tasks_block');
+    $this->drupalPlaceBlock('page_title_block');
+
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer taxonomy',
+      'access taxonomy overview',
+      'bypass node access',
+    ]));
+    $this->vocabulary = $this->createVocabulary();
+
+    $field_name = 'taxonomy_' . $this->vocabulary->id();
+
+    $handler_settings = [
+      'target_bundles' => [
+        $this->vocabulary->id() => $this->vocabulary->id(),
+      ],
+      'auto_create' => TRUE,
+    ];
+    $this->createEntityReferenceField('node', 'article', $field_name, NULL, 'taxonomy_term', 'default', $handler_settings, FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED);
+    $this->field = FieldConfig::loadByName('node', 'article', $field_name);
+
+    /** @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface $display_repository */
+    $display_repository = \Drupal::service('entity_display.repository');
+    $display_repository->getFormDisplay('node', 'article')
+      ->setComponent($field_name, [
+        'type' => 'options_select',
+      ])
+      ->save();
+    $display_repository->getViewDisplay('node', 'article')
+      ->setComponent($field_name, [
+        'type' => 'entity_reference_label',
+      ])
+      ->save();
+  }
+
+  /**
+   * The "parent" field must restrict references to the same vocabulary.
+   */
+  public function testParentHandlerSettings(): void {
+    $vocabulary_fields = \Drupal::service('entity_field.manager')->getFieldDefinitions('taxonomy_term', $this->vocabulary->id());
+    $parent_target_bundles = $vocabulary_fields['parent']->getSetting('handler_settings')['target_bundles'];
+    $this->assertSame([$this->vocabulary->id() => $this->vocabulary->id()], $parent_target_bundles);
+  }
+
+  /**
+   * Tests terms in a single and multiple hierarchy.
+   */
+  public function testTaxonomyTermHierarchy(): void {
+    // Create two taxonomy terms.
+    $term1 = $this->createTerm($this->vocabulary);
+    $term2 = $this->createTerm($this->vocabulary);
+
+    // Get the taxonomy storage.
+    /** @var \Drupal\taxonomy\TermStorageInterface $taxonomy_storage */
+    $taxonomy_storage = $this->container->get('entity_type.manager')->getStorage('taxonomy_term');
+
+    // Check that hierarchy is flat.
+    $this->assertEquals(0, $taxonomy_storage->getVocabularyHierarchyType($this->vocabulary->id()), 'Vocabulary is flat.');
+
+    // Edit $term2, setting $term1 as parent.
+    $edit = [];
+    $edit['parent[]'] = [$term1->id()];
+    $this->drupalGet('taxonomy/term/' . $term2->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+
+    // Check the hierarchy.
+    $children = $taxonomy_storage->loadChildren($term1->id());
+    $parents = $taxonomy_storage->loadParents($term2->id());
+    $this->assertTrue(isset($children[$term2->id()]), 'Child found correctly.');
+    $this->assertTrue(isset($parents[$term1->id()]), 'Parent found correctly.');
+
+    // Load and save a term, confirming that parents are still set.
+    $term = Term::load($term2->id());
+    $term->save();
+    $parents = $taxonomy_storage->loadParents($term2->id());
+    $this->assertTrue(isset($parents[$term1->id()]), 'Parent found correctly.');
+
+    // Create a third term and save this as a parent of term2.
+    $term3 = $this->createTerm($this->vocabulary);
+    $term2->parent = [$term1->id(), $term3->id()];
+    $term2->save();
+    $parents = $taxonomy_storage->loadParents($term2->id());
+    $this->assertArrayHasKey($term1->id(), $parents);
+    $this->assertArrayHasKey($term3->id(), $parents);
+  }
+
+  /**
+   * Tests that many terms with parents show on each page.
+   */
+  public function testTaxonomyTermChildTerms(): void {
+    // Set limit to 10 terms per page. Set variable to 9 so 10 terms appear.
+    $this->config('taxonomy.settings')->set('terms_per_page_admin', '9')->save();
+    $term1 = $this->createTerm($this->vocabulary);
+    $terms_array = [];
+
+    $taxonomy_storage = $this->container->get('entity_type.manager')->getStorage('taxonomy_term');
+
+    // Create 40 terms. Terms 1-12 get parent of $term1. All others are
+    // individual terms.
+    for ($x = 1; $x <= 40; $x++) {
+      $edit = [];
+      // Set terms in order so we know which terms will be on which pages.
+      $edit['weight'] = $x;
+
+      // Set terms 1-20 to be children of first term created.
+      if ($x <= 12) {
+        $edit['parent'] = $term1->id();
+      }
+      $term = $this->createTerm($this->vocabulary, $edit);
+      $children = $taxonomy_storage->loadChildren($term1->id());
+      $parents = $taxonomy_storage->loadParents($term->id());
+      $terms_array[$x] = Term::load($term->id());
+    }
+
+    // Get Page 1. Parent term and terms 1-13 are displayed.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+    $this->assertSession()->pageTextContains($term1->getName());
+    for ($x = 1; $x <= 13; $x++) {
+      $this->assertSession()->pageTextContains($terms_array[$x]->getName());
+    }
+
+    // Get Page 2. Parent term and terms 1-18 are displayed.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview', ['query' => ['page' => 1]]);
+    $this->assertSession()->pageTextContains($term1->getName());
+    for ($x = 1; $x <= 18; $x++) {
+      $this->assertSession()->pageTextContains($terms_array[$x]->getName());
+    }
+
+    // Get Page 3. No parent term and no terms <18 are displayed. Terms 18-25
+    // are displayed.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview', ['query' => ['page' => 2]]);
+    $this->assertSession()->pageTextNotContains($term1->getName());
+    for ($x = 1; $x <= 17; $x++) {
+      $this->assertSession()->pageTextNotContains($terms_array[$x]->getName());
+    }
+    for ($x = 18; $x <= 25; $x++) {
+      $this->assertSession()->pageTextContains($terms_array[$x]->getName());
+    }
+  }
+
+  /**
+   * Tests term creation with a free-tagging vocabulary from the node form.
+   */
+  public function testNodeTermCreationAndDeletion(): void {
+    // Enable tags in the vocabulary.
+    $field = $this->field;
+    \Drupal::service('entity_display.repository')
+      ->getFormDisplay($field->getTargetEntityTypeId(), $field->getTargetBundle())
+      ->setComponent($field->getName(), [
+        'type' => 'entity_reference_autocomplete_tags',
+        'settings' => [
+          'placeholder' => 'Start typing here.',
+        ],
+      ])
+      ->save();
+    // Prefix the terms with a letter to ensure there is no clash in the first
+    // three letters.
+    // @see https://www.drupal.org/node/2397691
+    $terms = [
+      'term1' => 'a' . $this->randomMachineName(),
+      'term2' => 'b' . $this->randomMachineName(),
+      'term3' => 'c' . $this->randomMachineName() . ', ' . $this->randomMachineName(),
+      'term4' => 'd' . $this->randomMachineName(),
+    ];
+
+    $edit = [];
+    $edit['title[0][value]'] = $this->randomMachineName();
+    $edit['body[0][value]'] = $this->randomMachineName();
+    // Insert the terms in a comma separated list. Vocabulary 1 is a
+    // free-tagging field created by the default profile.
+    $edit[$field->getName() . '[target_id]'] = Tags::implode($terms);
+
+    // Verify the placeholder is there.
+    $this->drupalGet('node/add/article');
+    $this->assertSession()->responseContains('placeholder="Start typing here."');
+
+    // Preview and verify the terms appear but are not created.
+    $this->submitForm($edit, 'Preview');
+    foreach ($terms as $term) {
+      $this->assertSession()->pageTextContains($term);
+    }
+    $tree = $this->container->get('entity_type.manager')->getStorage('taxonomy_term')->loadTree($this->vocabulary->id());
+    $this->assertEmpty($tree, 'The terms are not created on preview.');
+
+    // Save, creating the terms.
+    $this->drupalGet('node/add/article');
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextContains('Article ' . $edit['title[0][value]'] . ' has been created.');
+
+    // Verify that the creation message contains a link to a node.
+    $this->assertSession()->elementExists('xpath', '//div[@data-drupal-messages]//a[contains(@href, "node/")]');
+
+    foreach ($terms as $term) {
+      $this->assertSession()->pageTextContains($term);
+    }
+
+    // Get the created terms.
+    $term_objects = [];
+    foreach ($terms as $key => $term) {
+      $term_objects[$key] = \Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadByProperties([
+        'name' => $term,
+      ]);
+      $term_objects[$key] = reset($term_objects[$key]);
+    }
+
+    // Get the node.
+    $node = $this->drupalGetNodeByTitle($edit['title[0][value]']);
+
+    // Test editing the node.
+    $this->drupalGet('node/' . $node->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+    foreach ($terms as $term) {
+      $this->assertSession()->pageTextContains($term);
+    }
+
+    // Delete term 1 from the term edit page.
+    $this->drupalGet('taxonomy/term/' . $term_objects['term1']->id() . '/edit');
+    $this->clickLink('Delete');
+    $this->submitForm([], 'Delete');
+
+    // Delete term 2 from the term delete page.
+    $this->drupalGet('taxonomy/term/' . $term_objects['term2']->id() . '/delete');
+    $this->submitForm([], 'Delete');
+
+    // Verify that the terms appear on the node page after the two terms were
+    // deleted.
+    $term_names = [$term_objects['term3']->getName(), $term_objects['term4']->getName()];
+    $this->drupalGet('node/' . $node->id());
+    foreach ($term_names as $term_name) {
+      $this->assertSession()->pageTextContains($term_name);
+    }
+    $this->assertSession()->pageTextNotContains($term_objects['term1']->getName());
+    $this->assertSession()->pageTextNotContains($term_objects['term2']->getName());
+  }
+
+  /**
+   * Save, edit and delete a term using the user interface.
+   */
+  public function testTermInterface(): void {
+    \Drupal::service('module_installer')->install(['views']);
+    $edit = [
+      'name[0][value]' => $this->randomMachineName(12),
+      'description[0][value]' => $this->randomMachineName(100),
+    ];
+    // Explicitly set the parents field to 'root', to ensure that
+    // TermForm::save() handles the invalid term ID correctly.
+    $edit['parent[]'] = [0];
+
+    // Create the term to edit.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    $this->submitForm($edit, 'Save');
+
+    // Ensure form redirected back to term add page.
+    $this->assertSession()->addressEquals('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+
+    $terms = \Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadByProperties([
+      'name' => $edit['name[0][value]'],
+    ]);
+    $term = reset($terms);
+    $this->assertNotNull($term, 'Term found in database.');
+
+    // Submitting a term takes us to the add page; we need the List page.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+
+    $this->clickLink('Edit', 1);
+
+    // Verify that the randomly generated term is present.
+    $this->assertSession()->pageTextContains($edit['name[0][value]']);
+    $this->assertSession()->pageTextContains($edit['description[0][value]']);
+
+    // Test the "Add child" link on the overview page.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+    $this->assertSession()->linkExistsExact('Add child');
+    $this->clickLink('Add child');
+    $edit = [
+      'name[0][value]' => 'Child term',
+    ];
+    $this->submitForm($edit, 'Save');
+    $terms = \Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadByProperties([
+      'name' => 'Child term',
+    ]);
+    $child = reset($terms);
+    $this->assertNotNull($child, 'Child term found in database.');
+    $this->assertEquals($term->id(), $child->get('parent')->getValue()[0]['target_id']);
+
+    // Edit the term.
+    $edit = [
+      'name[0][value]' => $this->randomMachineName(14),
+      'description[0][value]' => $this->randomMachineName(102),
+    ];
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+
+    // Ensure form redirected back to term view.
+    $this->assertSession()->addressEquals('taxonomy/term/' . $term->id());
+
+    // Check that the term is still present at admin UI after edit.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+    $this->assertSession()->pageTextContains($edit['name[0][value]']);
+    $this->assertSession()->linkExists('Edit');
+
+    // Unpublish the term.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $this->submitForm(["status[value]" => 0], 'Save');
+    // Check that the term is now unpublished in the list.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+    $this->assertSession()->elementTextContains('css', "#edit-terms-tid{$term->id()}0-status", 'Unpublished');
+
+    // Check the term link can be clicked through to the term page.
+    $this->clickLink($edit['name[0][value]']);
+    $this->assertSession()->statusCodeEquals(200);
+
+    // View the term and check that it is correct.
+    $this->drupalGet('taxonomy/term/' . $term->id());
+    $this->assertSession()->pageTextContains($edit['name[0][value]']);
+    $this->assertSession()->pageTextContains($edit['description[0][value]']);
+
+    // Did this page request display a 'term-listing-heading'?
+    $this->assertSession()->elementExists('xpath', '//div[@class="views-element-container"]/div/header/div/div/p');
+    // Check that it does NOT show a description when description is blank.
+    $term->setDescription(NULL);
+    $term->save();
+    $this->drupalGet('taxonomy/term/' . $term->id());
+    $this->assertSession()->elementNotExists('xpath', '//div[@class="views-element-container"]/div/header/div/div/p');
+
+    // Check that the description value is processed.
+    $value = $this->randomMachineName();
+    $term->setDescription($value);
+    $term->save();
+    $this->assertSame("<p>{$value}</p>\n", (string) $term->description->processed);
+
+    // Check that the term feed page is working.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/feed');
+
+    // Delete the term.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $this->clickLink('Delete');
+    $this->submitForm([], 'Delete');
+
+    // Assert that the term no longer exists.
+    $this->drupalGet('taxonomy/term/' . $term->id());
+    $this->assertSession()->statusCodeEquals(404);
+
+    // Test "save and go to list" action while creating term.
+    // Create the term to edit.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    $edit = [
+      'name[0][value]' => $this->randomMachineName(12),
+      'description[0][value]' => $this->randomMachineName(100),
+    ];
+
+    // Create the term to edit.
+    $this->submitForm($edit, 'Save and go to list');
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSession()->addressEquals('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+    $this->assertSession()->pageTextContains($edit['name[0][value]']);
+
+    // Validate that "Save and go to list" doesn't exist when destination
+    // parameter is present.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add', ['query' => ['destination' => 'node/add']]);
+    $this->assertSession()->pageTextNotContains('Save and go to list');
+
+    // Validate that "Save and go to list" doesn't exist when missing permission
+    // 'access taxonomy overview'.
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer taxonomy',
+      'bypass node access',
+    ]));
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    $this->assertSession()->pageTextNotContains('Save and go to list');
+  }
+
+  /**
+   * Test UI with override_selector TRUE.
+   */
+  public function testTermSaveOverrideSelector(): void {
+    $this->config('taxonomy.settings')->set('override_selector', TRUE)->save();
+
+    // Create a Term.
+    $edit = [
+      'name[0][value]' => $this->randomMachineName(12),
+      'description[0][value]' => $this->randomMachineName(100),
+    ];
+    // Create the term to edit.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    $this->submitForm($edit, 'Save');
+    $terms = \Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadByProperties([
+      'name' => $edit['name[0][value]'],
+    ]);
+    $term = reset($terms);
+    $this->assertNotNull($term, 'Term found in database.');
+
+    // The term appears on the vocab list page.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+    $this->assertSession()->pageTextContains($term->getName());
+  }
+
+  /**
+   * Save, edit and delete a term using the user interface.
+   */
+  public function testTermReorder(): void {
+    $assert = $this->assertSession();
+    $this->createTerm($this->vocabulary);
+    $this->createTerm($this->vocabulary);
+    $this->createTerm($this->vocabulary);
+
+    $taxonomy_storage = $this->container->get('entity_type.manager')->getStorage('taxonomy_term');
+
+    // Fetch the created terms in the default alphabetical order, i.e. term1
+    // precedes term2 alphabetically, and term2 precedes term3.
+    $taxonomy_storage->resetCache();
+    [$term1, $term2, $term3] = $taxonomy_storage->loadTree($this->vocabulary->id(), 0, NULL, TRUE);
+
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+
+    // Each term has four hidden fields, "tid:1:0[tid]", "tid:1:0[parent]",
+    // "tid:1:0[depth]", and "tid:1:0[weight]". Change the order to term2,
+    // term3, term1 by setting weight property, make term3 a child of term2 by
+    // setting the parent and depth properties, and update all hidden fields.
+    $hidden_edit = [
+      'terms[tid:' . $term2->id() . ':0][term][tid]' => $term2->id(),
+      'terms[tid:' . $term2->id() . ':0][term][parent]' => 0,
+      'terms[tid:' . $term2->id() . ':0][term][depth]' => 0,
+      'terms[tid:' . $term3->id() . ':0][term][tid]' => $term3->id(),
+      'terms[tid:' . $term3->id() . ':0][term][parent]' => $term2->id(),
+      'terms[tid:' . $term3->id() . ':0][term][depth]' => 1,
+      'terms[tid:' . $term1->id() . ':0][term][tid]' => $term1->id(),
+      'terms[tid:' . $term1->id() . ':0][term][parent]' => 0,
+      'terms[tid:' . $term1->id() . ':0][term][depth]' => 0,
+    ];
+    // Because we can't post hidden form elements, we have to change them in
+    // code here, and then submit.
+    foreach ($hidden_edit as $field => $value) {
+      $node = $assert->hiddenFieldExists($field);
+      $node->setValue($value);
+    }
+    // Edit non-hidden elements within submitForm().
+    $edit = [
+      'terms[tid:' . $term2->id() . ':0][weight]' => 0,
+      'terms[tid:' . $term3->id() . ':0][weight]' => 1,
+      'terms[tid:' . $term1->id() . ':0][weight]' => 2,
+    ];
+    $this->submitForm($edit, 'Save');
+
+    $taxonomy_storage->resetCache();
+    $terms = $taxonomy_storage->loadTree($this->vocabulary->id());
+    $this->assertEquals($term2->id(), $terms[0]->tid, 'Term 2 was moved above term 1.');
+    $this->assertEquals([$term2->id()], $terms[1]->parents, 'Term 3 was made a child of term 2.');
+    $this->assertEquals($term1->id(), $terms[2]->tid, 'Term 1 was moved below term 2.');
+
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+    $this->submitForm([], 'Reset to alphabetical');
+    // Submit confirmation form.
+    $this->submitForm([], 'Reset to alphabetical');
+    // Ensure form redirected back to overview.
+    $this->assertSession()->addressEquals('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+
+    $taxonomy_storage->resetCache();
+    $terms = $taxonomy_storage->loadTree($this->vocabulary->id(), 0, NULL, TRUE);
+    $this->assertEquals($term1->id(), $terms[0]->id(), 'Term 1 was moved to back above term 2.');
+    $this->assertEquals($term2->id(), $terms[1]->id(), 'Term 2 was moved to back below term 1.');
+    $this->assertEquals($term3->id(), $terms[2]->id(), 'Term 3 is still below term 2.');
+    $this->assertEquals([$term2->id()], $terms[2]->parents, 'Term 3 is still a child of term 2.');
+  }
+
+  /**
+   * Tests saving a term with multiple parents through the UI.
+   */
+  public function testTermMultipleParentsInterface(): void {
+    // Add two new terms to the vocabulary so that we can have multiple parents.
+    // These will be terms with tids of 1 and 2 respectively.
+    $this->createTerm($this->vocabulary);
+    $this->createTerm($this->vocabulary);
+
+    // Add a new term with multiple parents.
+    $edit = [
+      'name[0][value]' => $this->randomMachineName(12),
+      'description[0][value]' => $this->randomMachineName(100),
+      'parent[]' => [0, 1],
+    ];
+    // Save the new term.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    $this->submitForm($edit, 'Save');
+
+    // Check that the term was successfully created.
+    $term = $this->reloadTermByName($edit['name[0][value]']);
+    $this->assertNotNull($term, 'Term found in database.');
+    $this->assertEquals($edit['name[0][value]'], $term->getName(), 'Term name was successfully saved.');
+    $this->assertEquals($edit['description[0][value]'], $term->getDescription(), 'Term description was successfully saved.');
+
+    // Check that we have the expected parents.
+    $this->assertEquals([0, 1], $this->getParentTids($term), 'Term parents (root plus one) were successfully saved.');
+
+    // Load the edit form and save again to ensure parent are preserved.
+    // Generate a new name, so we know that the term really is saved.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $edit = [
+      'name[0][value]' => $this->randomMachineName(12),
+    ];
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextContains('Updated term ' . $edit['name[0][value]']);
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $this->submitForm([], 'Save');
+    $this->assertSession()->pageTextContains('Updated term ' . $edit['name[0][value]']);
+
+    // Check that we still have the expected parents.
+    $term = $this->reloadTermByName($edit['name[0][value]']);
+    $this->assertEquals([0, 1], $this->getParentTids($term), 'Term parents (root plus one) were successfully saved again.');
+
+    // Save with two real parents. i.e., not including <root>.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $edit = [
+      'name[0][value]' => $this->randomMachineName(12),
+      'parent[]' => [1, 2],
+    ];
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextContains('Updated term ' . $edit['name[0][value]']);
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $this->submitForm([], 'Save');
+    $this->assertSession()->pageTextContains('Updated term ' . $edit['name[0][value]']);
+
+    // Check that we have the expected parents.
+    $term = $this->reloadTermByName($edit['name[0][value]']);
+    $this->assertEquals([1, 2], $this->getParentTids($term), 'Term parents (two real) were successfully saved.');
+  }
+
+  /**
+   * Reloads a term by name.
+   *
+   * @param string $name
+   *   The name of the term.
+   *
+   * @return \Drupal\taxonomy\TermInterface
+   *   The reloaded term.
+   */
+  private function reloadTermByName(string $name): TermInterface {
+    \Drupal::entityTypeManager()->getStorage('taxonomy_term')->resetCache();
+    /** @var \Drupal\taxonomy\TermInterface[] $terms */
+    $terms = \Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadByProperties(['name' => $name]);
+    return reset($terms);
+  }
+
+  /**
+   * Get the parent tids for a term including root.
+   *
+   * @param \Drupal\taxonomy\TermInterface $term
+   *   The term.
+   *
+   * @return array
+   *   A sorted array of tids and 0 if the root is a parent.
+   */
+  private function getParentTids($term) {
+    $parent_tids = [];
+    foreach ($term->get('parent') as $item) {
+      $parent_tids[] = (int) $item->target_id;
+    }
+    sort($parent_tids);
+
+    return $parent_tids;
+  }
+
+  /**
+   * Tests that editing and saving a node with no changes works correctly.
+   */
+  public function testReSavingTags(): void {
+    // Enable tags in the vocabulary.
+    $field = $this->field;
+    \Drupal::service('entity_display.repository')
+      ->getFormDisplay($field->getTargetEntityTypeId(), $field->getTargetBundle())
+      ->setComponent($field->getName(), [
+        'type' => 'entity_reference_autocomplete_tags',
+      ])
+      ->save();
+
+    // Create a term and a node using it.
+    $term = $this->createTerm($this->vocabulary);
+    $edit = [];
+    $edit['title[0][value]'] = $this->randomMachineName(8);
+    $edit['body[0][value]'] = $this->randomMachineName(16);
+    $edit[$this->field->getName() . '[target_id]'] = $term->getName();
+    $this->drupalGet('node/add/article');
+    $this->submitForm($edit, 'Save');
+
+    // Check that the term is displayed when editing and saving the node with no
+    // changes.
+    $this->clickLink('Edit');
+    $this->assertSession()->responseContains($term->getName());
+    $this->submitForm([], 'Save');
+    $this->assertSession()->responseContains($term->getName());
+  }
+
+  /**
+   * Check the breadcrumb on edit and delete a term page.
+   */
+  public function testTermBreadcrumbs(): void {
+    $edit = [
+      'name[0][value]' => $this->randomMachineName(14),
+      'description[0][value]' => $this->randomMachineName(100),
+      'parent[]' => [0],
+    ];
+
+    // Create the term.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add');
+    $this->submitForm($edit, 'Save');
+
+    $terms = \Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadByProperties([
+      'name' => $edit['name[0][value]'],
+    ]);
+    $term = reset($terms);
+    $this->assertNotNull($term, 'Term found in database.');
+
+    // Check the breadcrumb on the term edit page.
+    $trail = [
+      '' => 'Home',
+      'taxonomy/term/' . $term->id() => $term->label(),
+    ];
+    $this->assertBreadcrumb('taxonomy/term/' . $term->id() . '/edit', $trail);
+    $this->assertSession()->assertEscaped($term->label());
+
+    // Check the breadcrumb on the term delete page.
+    $trail = [
+      '' => 'Home',
+      'taxonomy/term/' . $term->id() => $term->label(),
+    ];
+    $this->assertBreadcrumb('taxonomy/term/' . $term->id() . '/delete', $trail);
+    $this->assertSession()->assertEscaped($term->label());
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TermTranslationFieldViewTest.php

@@ -0,0 +1,117 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\node\Entity\Node;
+
+/**
+ * Tests the translation of taxonomy terms field on nodes.
+ *
+ * @group taxonomy
+ */
+class TermTranslationFieldViewTest extends TaxonomyTestBase {
+
+  use TaxonomyTranslationTestTrait;
+
+  /**
+   * The term that should be translated.
+   *
+   * @var \Drupal\taxonomy\Entity\Term
+   */
+  protected $term;
+
+  /**
+   * The tag in the source language.
+   *
+   * @var string
+   */
+  protected $baseTagName = 'OriginalTagName';
+
+  /**
+   * The translated value for the tag.
+   *
+   * @var string
+   */
+  protected $translatedTagName = 'TranslatedTagName';
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['language', 'content_translation', 'taxonomy'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->setupLanguages();
+    $this->vocabulary = $this->createVocabulary();
+    $this->enableTranslation();
+    $this->setUpTerm();
+    $this->setUpTermReferenceField();
+    $this->setUpNode();
+  }
+
+  /**
+   * Tests if the translated taxonomy term is displayed.
+   */
+  public function testTranslatedTaxonomyTermReferenceDisplay(): void {
+    $path = 'node/' . $this->node->id();
+    $translation_path = $this->translateToLangcode . '/' . $path;
+
+    $this->drupalGet($path);
+    $this->assertSession()->pageTextNotContains($this->translatedTagName);
+    $this->assertSession()->pageTextContains($this->baseTagName);
+    $this->drupalGet($translation_path);
+    $this->assertSession()->pageTextContains($this->translatedTagName);
+    $this->assertSession()->pageTextNotContains($this->baseTagName);
+  }
+
+  /**
+   * Creates a test subject node, with translation.
+   */
+  protected function setUpNode() {
+    /** @var \Drupal\node\Entity\Node $node */
+    $node = Node::create([
+      'title' => $this->randomMachineName(),
+      'type' => 'article',
+      'description' => [
+        [
+          'value' => $this->randomMachineName(),
+          'format' => 'basic_html',
+        ],
+      ],
+      $this->termFieldName => [['target_id' => $this->term->id()]],
+      'langcode' => $this->baseLangcode,
+    ]);
+    $node->save();
+    $node->addTranslation($this->translateToLangcode, $node->toArray());
+    $node->save();
+    $this->node = $node;
+  }
+
+  /**
+   * Creates a test subject term, with translation.
+   */
+  protected function setUpTerm() {
+    $this->term = $this->createTerm($this->vocabulary, [
+      'name' => $this->baseTagName,
+      'langcode' => $this->baseLangcode,
+    ]);
+
+    $this->term->addTranslation($this->translateToLangcode, [
+      'name' => $this->translatedTagName,
+    ]);
+    $this->term->save();
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TermTranslationTest.php

@@ -0,0 +1,157 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Core\Url;
+use Drupal\Tests\system\Functional\Menu\AssertBreadcrumbTrait;
+
+/**
+ * Tests for proper breadcrumb translation.
+ *
+ * @group taxonomy
+ */
+class TermTranslationTest extends TaxonomyTestBase {
+
+  use AssertBreadcrumbTrait;
+  use TaxonomyTranslationTestTrait;
+
+  /**
+   * Term to translated term mapping.
+   *
+   * @var array
+   */
+  protected $termTranslationMap = [
+    'one' => 'translatedOne',
+    'two' => 'translatedTwo',
+    'three' => 'translatedThree',
+  ];
+
+  /**
+   * Created terms.
+   *
+   * @var \Drupal\taxonomy\Entity\Term[]
+   */
+  protected $terms = [];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['taxonomy', 'language', 'content_translation'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->setupLanguages();
+    $this->vocabulary = $this->createVocabulary();
+    $this->enableTranslation();
+    $this->setUpTerms();
+    $this->setUpTermReferenceField();
+  }
+
+  /**
+   * Tests translated breadcrumbs.
+   */
+  public function testTranslatedBreadcrumbs(): void {
+    // Ensure non-translated breadcrumb is correct.
+    $breadcrumb = [Url::fromRoute('<front>')->toString() => 'Home'];
+    foreach ($this->terms as $term) {
+      $breadcrumb[$term->toUrl()->toString()] = $term->label();
+    }
+    // The last item will not be in the breadcrumb.
+    array_pop($breadcrumb);
+
+    // Check the breadcrumb on the leaf term page.
+    $term = $this->getLeafTerm();
+    $this->assertBreadcrumb($term->toUrl(), $breadcrumb, $term->label());
+
+    $languages = \Drupal::languageManager()->getLanguages();
+
+    // Construct the expected translated breadcrumb.
+    $breadcrumb = [Url::fromRoute('<front>', [], ['language' => $languages[$this->translateToLangcode]])->toString() => 'Home'];
+    foreach ($this->terms as $term) {
+      $translated = $term->getTranslation($this->translateToLangcode);
+      $url = $translated->toUrl('canonical', ['language' => $languages[$this->translateToLangcode]])->toString();
+      $breadcrumb[$url] = $translated->label();
+    }
+    array_pop($breadcrumb);
+
+    // Check for the translated breadcrumb on the translated leaf term page.
+    $term = $this->getLeafTerm();
+    $translated = $term->getTranslation($this->translateToLangcode);
+    $this->assertBreadcrumb($translated->toUrl('canonical', ['language' => $languages[$this->translateToLangcode]]), $breadcrumb, $translated->label());
+
+  }
+
+  /**
+   * Tests translation of terms are showed in the node.
+   */
+  public function testTermsTranslation(): void {
+
+    // Set the display of the term reference field on the article content type
+    // to "Check boxes/radio buttons".
+    \Drupal::service('entity_display.repository')
+      ->getFormDisplay('node', 'article')
+      ->setComponent($this->termFieldName, [
+        'type' => 'options_buttons',
+      ])
+      ->save();
+    $this->drupalLogin($this->drupalCreateUser(['create article content']));
+
+    // Test terms are listed.
+    $this->drupalGet('node/add/article');
+    $this->assertSession()->pageTextContains('one');
+    $this->assertSession()->pageTextContains('two');
+    $this->assertSession()->pageTextContains('three');
+
+    // Test terms translated are listed.
+    $this->drupalGet('hu/node/add/article');
+    $this->assertSession()->pageTextContains('translatedOne');
+    $this->assertSession()->pageTextContains('translatedTwo');
+    $this->assertSession()->pageTextContains('translatedThree');
+  }
+
+  /**
+   * Setup translated terms in a hierarchy.
+   */
+  protected function setUpTerms() {
+    $parent_vid = 0;
+    foreach ($this->termTranslationMap as $name => $translation) {
+
+      $term = $this->createTerm($this->vocabulary, [
+        'name' => $name,
+        'langcode' => $this->baseLangcode,
+        'parent' => $parent_vid,
+      ]);
+
+      $term->addTranslation($this->translateToLangcode, [
+        'name' => $translation,
+      ]);
+      $term->save();
+
+      // Each term is nested under the last.
+      $parent_vid = $term->id();
+
+      $this->terms[] = $term;
+    }
+  }
+
+  /**
+   * Get the final (leaf) term in the hierarchy.
+   *
+   * @return \Drupal\taxonomy\Entity\Term
+   *   The final term in the hierarchy.
+   */
+  protected function getLeafTerm() {
+    return $this->terms[count($this->termTranslationMap) - 1];
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/TermTranslationUITest.php

@@ -0,0 +1,223 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Tests\content_translation\Functional\ContentTranslationUITestBase;
+use Drupal\Core\Language\LanguageInterface;
+use Drupal\taxonomy\Entity\Vocabulary;
+
+/**
+ * Tests the Term Translation UI.
+ *
+ * @group taxonomy
+ */
+class TermTranslationUITest extends ContentTranslationUITestBase {
+
+  /**
+   * The vocabulary used for creating terms.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultCacheContexts = [
+    'languages:language_interface',
+    'theme',
+    'url.query_args:_wrapper_format',
+    'user.permissions',
+    'url.site',
+  ];
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['language', 'content_translation', 'taxonomy'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    $this->entityTypeId = 'taxonomy_term';
+    $this->bundle = 'tags';
+    parent::setUp();
+    $this->doSetup();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setupBundle() {
+    parent::setupBundle();
+
+    // Create a vocabulary.
+    $this->vocabulary = Vocabulary::create([
+      'name' => $this->bundle,
+      'description' => $this->randomMachineName(),
+      'vid' => $this->bundle,
+      'langcode' => LanguageInterface::LANGCODE_NOT_SPECIFIED,
+      'weight' => mt_rand(0, 10),
+    ]);
+    $this->vocabulary->save();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getTranslatorPermissions() {
+    return array_merge(parent::getTranslatorPermissions(), ['administer taxonomy']);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getNewEntityValues($langcode) {
+    return ['name' => $this->randomMachineName()] + parent::getNewEntityValues($langcode);
+  }
+
+  /**
+   * Returns an edit array containing the values to be posted.
+   */
+  protected function getEditValues($values, $langcode, $new = FALSE) {
+    $edit = parent::getEditValues($values, $langcode, $new);
+
+    // To be able to post values for the configurable base fields (name,
+    // description) have to be suffixed with [0][value].
+    foreach ($edit as $property => $value) {
+      foreach (['name', 'description'] as $key) {
+        if ($property == $key) {
+          $edit[$key . '[0][value]'] = $value;
+          unset($edit[$property]);
+        }
+      }
+    }
+    return $edit;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function testTranslationUI(): void {
+    parent::testTranslationUI();
+
+    // Make sure that no row was inserted for taxonomy vocabularies which do
+    // not have translations enabled.
+    $tids = \Drupal::entityQueryAggregate('taxonomy_term')
+      ->accessCheck(FALSE)
+      ->aggregate('tid', 'COUNT')
+      ->condition('vid', $this->bundle, '<>')
+      ->groupBy('tid')
+      ->execute();
+
+    foreach ($tids as $tid) {
+      $this->assertTrue($tid['tid_count'] < 2, 'Term does have translations.');
+    }
+  }
+
+  /**
+   * Tests translate link on vocabulary term list.
+   */
+  public function testTranslateLinkVocabularyAdminPage(): void {
+    $this->drupalLogin($this->drupalCreateUser(array_merge(parent::getTranslatorPermissions(), ['access administration pages', 'administer taxonomy'])));
+
+    $values = [
+      'name' => $this->randomMachineName(),
+    ];
+    $translatable_tid = $this->createEntity($values, $this->langcodes[0], $this->vocabulary->id());
+
+    // Create an untranslatable vocabulary.
+    $untranslatable_vocabulary = Vocabulary::create([
+      'name' => 'untranslatable_voc',
+      'description' => $this->randomMachineName(),
+      'vid' => 'untranslatable_voc',
+      'langcode' => LanguageInterface::LANGCODE_NOT_SPECIFIED,
+      'weight' => mt_rand(0, 10),
+    ]);
+    $untranslatable_vocabulary->save();
+
+    $values = [
+      'name' => $this->randomMachineName(),
+    ];
+    $untranslatable_tid = $this->createEntity($values, $this->langcodes[0], $untranslatable_vocabulary->id());
+
+    // Verify translation links.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/overview');
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSession()->linkByHrefExists('term/' . $translatable_tid . '/translations', 0, 'The translations link exists for a translatable vocabulary.');
+    $this->assertSession()->linkByHrefExists('term/' . $translatable_tid . '/edit', 0, 'The edit link exists for a translatable vocabulary.');
+
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $untranslatable_vocabulary->id() . '/overview');
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSession()->linkByHrefExists('term/' . $untranslatable_tid . '/edit');
+    $this->assertSession()->linkByHrefNotExists('term/' . $untranslatable_tid . '/translations');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function doTestTranslationEdit() {
+    $storage = $this->container->get('entity_type.manager')
+      ->getStorage($this->entityTypeId);
+    $storage->resetCache([$this->entityId]);
+    $entity = $storage->load($this->entityId);
+    $languages = $this->container->get('language_manager')->getLanguages();
+
+    foreach ($this->langcodes as $langcode) {
+      // We only want to test the title for non-english translations.
+      if ($langcode != 'en') {
+        $options = ['language' => $languages[$langcode]];
+        $url = $entity->toUrl('edit-form', $options);
+        $this->drupalGet($url);
+        $this->assertSession()->pageTextContains("{$entity->getTranslation($langcode)->label()} [{$languages[$langcode]->getName()} translation]");
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function doTestPublishedStatus() {
+    $storage = $this->container->get('entity_type.manager')
+      ->getStorage($this->entityTypeId);
+    $storage->resetCache([$this->entityId]);
+    $entity = $storage->load($this->entityId);
+    $languages = $this->container->get('language_manager')->getLanguages();
+
+    $statuses = [
+      TRUE,
+      FALSE,
+    ];
+
+    foreach ($statuses as $index => $value) {
+      // (Un)publish the term translations and check that the translation
+      // statuses are (un)published accordingly.
+      foreach ($this->langcodes as $langcode) {
+        $options = ['language' => $languages[$langcode]];
+        $url = $entity->toUrl('edit-form', $options);
+        $this->drupalGet($url, $options);
+        $this->submitForm(['status[value]' => $value], 'Save');
+      }
+      $storage->resetCache([$this->entityId]);
+      $entity = $storage->load($this->entityId);
+      foreach ($this->langcodes as $langcode) {
+        // The term is created as unpublished thus we switch to the published
+        // status first.
+        $status = !$index;
+        $translation = $entity->getTranslation($langcode);
+        $this->assertEquals($status, $this->manager->getTranslationMetadata($translation)->isPublished(), 'The translation has been correctly unpublished.');
+      }
+    }
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/ThemeTest.php

@@ -0,0 +1,68 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+/**
+ * Verifies that various taxonomy pages use the expected theme.
+ *
+ * @group taxonomy
+ */
+class ThemeTest extends TaxonomyTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    // Make sure we are using distinct default and administrative themes for
+    // the duration of these tests.
+    \Drupal::service('theme_installer')->install(['olivero', 'claro']);
+    $this->config('system.theme')
+      ->set('default', 'olivero')
+      ->set('admin', 'claro')
+      ->save();
+
+    // Create and log in as a user who has permission to add and edit taxonomy
+    // terms and view the administrative theme.
+    $admin_user = $this->drupalCreateUser([
+      'administer taxonomy',
+      'view the administration theme',
+    ]);
+    $this->drupalLogin($admin_user);
+  }
+
+  /**
+   * Tests the theme used when adding, viewing and editing taxonomy terms.
+   */
+  public function testTaxonomyTermThemes(): void {
+    // Adding a term to a vocabulary is considered an administrative action and
+    // should use the administrative theme.
+    $vocabulary = $this->createVocabulary();
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary->id() . '/add');
+    // Check that the administrative theme's CSS appears on the page for adding
+    // a taxonomy term.
+    $this->assertSession()->responseContains('claro/css/base/elements.css');
+
+    // Viewing a taxonomy term should use the default theme.
+    $term = $this->createTerm($vocabulary);
+    $this->drupalGet('taxonomy/term/' . $term->id());
+    // Check that the default theme's CSS appears on the page for viewing
+    // a taxonomy term.
+    $this->assertSession()->responseContains('olivero/css/base/base.css');
+
+    // Editing a taxonomy term should use the same theme as adding one.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    // Check that the administrative theme's CSS appears on the page for editing
+    // a taxonomy term.
+    $this->assertSession()->responseContains('claro/css/base/elements.css');
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Update/NullDescriptionTest.php

@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Update;
+
+use Drupal\FunctionalTests\Update\UpdatePathTestBase;
+use Drupal\taxonomy\Entity\Vocabulary;
+
+/**
+ * Tests the upgrade path for making vocabularies' description NULL.
+ *
+ * @group taxonomy
+ * @see taxonomy_post_update_set_vocabulary_description_to_null()
+ */
+class NullDescriptionTest extends UpdatePathTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setDatabaseDumpFiles() {
+    $this->databaseDumpFiles = [
+      __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-9.4.0.filled.standard.php.gz',
+      __DIR__ . '/../../../fixtures/update/remove-description-from-tags-vocabulary.php',
+    ];
+  }
+
+  /**
+   * Tests the upgrade path for updating empty description to NULL.
+   */
+  public function testRunUpdates(): void {
+    $vocabulary = Vocabulary::load('tags');
+    $this->assertInstanceOf(Vocabulary::class, $vocabulary);
+
+    $this->assertSame("\n", $vocabulary->get('description'));
+    $this->runUpdates();
+
+    $vocabulary = Vocabulary::load('tags');
+    $this->assertInstanceOf(Vocabulary::class, $vocabulary);
+
+    $this->assertNull($vocabulary->get('description'));
+    $this->assertSame('', $vocabulary->getDescription());
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TaxonomyDefaultArgumentTest.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+/**
+ * Tests the representative node relationship for terms.
+ *
+ * @group taxonomy
+ */
+class TaxonomyDefaultArgumentTest extends TaxonomyTestBase {
+
+  /**
+   * Views used by this test.
+   *
+   * @var array
+   */
+  public static $testViews = ['taxonomy_default_argument_test'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Tests escaping of page title when the taxonomy plugin provides it.
+   */
+  public function testTermTitleEscaping(): void {
+    $this->term1->setName('<em>Markup</em>')->save();
+    $this->drupalGet('taxonomy_default_argument_test/' . $this->term1->id());
+    $this->assertSession()->assertEscaped($this->term1->label());
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TaxonomyFieldAllTermsTest.php

@@ -0,0 +1,78 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+use Drupal\views\Views;
+use Drupal\taxonomy\Entity\Vocabulary;
+
+/**
+ * Tests the "All terms" taxonomy term field handler.
+ *
+ * @group taxonomy
+ */
+class TaxonomyFieldAllTermsTest extends TaxonomyTestBase {
+
+  /**
+   * Views used by this test.
+   *
+   * @var array
+   */
+  public static $testViews = ['taxonomy_all_terms_test'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Tests the "all terms" field handler.
+   */
+  public function testViewsHandlerAllTermsField(): void {
+    $this->term1->setName('<em>Markup</em>')->save();
+    $view = Views::getView('taxonomy_all_terms_test');
+    $this->executeView($view);
+    $this->drupalGet('taxonomy_all_terms_test');
+
+    // Test term1 links.
+    $xpath = '//a[@href="' . $this->term1->toUrl()->toString() . '"]';
+    $this->assertSession()->elementsCount('xpath', $xpath, 2);
+    $links = $this->xpath($xpath);
+    $this->assertEquals($this->term1->label(), $links[0]->getText());
+    $this->assertEquals($this->term1->label(), $links[1]->getText());
+    $this->assertSession()->assertEscaped($this->term1->label());
+
+    // Test term2 links.
+    $xpath = '//a[@href="' . $this->term2->toUrl()->toString() . '"]';
+    $this->assertSession()->elementsCount('xpath', $xpath, 2);
+    $links = $this->xpath($xpath);
+    $this->assertEquals($this->term2->label(), $links[0]->getText());
+    $this->assertEquals($this->term2->label(), $links[1]->getText());
+  }
+
+  /**
+   * Tests token replacement in the "all terms" field handler.
+   */
+  public function testViewsHandlerAllTermsWithTokens(): void {
+    $view = Views::getView('taxonomy_all_terms_test');
+    $this->drupalGet('taxonomy_all_terms_token_test');
+
+    // Term itself: {{ term_node_tid }}
+    $this->assertSession()->pageTextContains('Term: ' . $this->term1->getName());
+
+    // The taxonomy term ID for the term: {{ term_node_tid__tid }}
+    $this->assertSession()->pageTextContains('The taxonomy term ID for the term: ' . $this->term1->id());
+
+    // The taxonomy term name for the term: {{ term_node_tid__name }}
+    $this->assertSession()->pageTextContains('The taxonomy term name for the term: ' . $this->term1->getName());
+
+    // The machine name for the vocabulary the term belongs to: {{ term_node_tid__vocabulary_vid }}
+    $this->assertSession()->pageTextContains('The machine name for the vocabulary the term belongs to: ' . $this->term1->bundle());
+
+    // The name for the vocabulary the term belongs to: {{ term_node_tid__vocabulary }}
+    $vocabulary = Vocabulary::load($this->term1->bundle());
+    $this->assertSession()->pageTextContains('The name for the vocabulary the term belongs to: ' . $vocabulary->label());
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TaxonomyFieldFilterTest.php

@@ -0,0 +1,203 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+use Drupal\Core\Language\LanguageInterface;
+use Drupal\field\Entity\FieldConfig;
+use Drupal\language\Entity\ConfigurableLanguage;
+use Drupal\Tests\views\Functional\ViewTestBase;
+use Drupal\views\Tests\ViewTestData;
+use Drupal\views\Views;
+use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\taxonomy\Entity\Vocabulary;
+use Drupal\taxonomy\Entity\Term;
+
+/**
+ * Tests taxonomy field filters with translations.
+ *
+ * @group taxonomy
+ */
+class TaxonomyFieldFilterTest extends ViewTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'language',
+    'taxonomy',
+    'taxonomy_test_views',
+    'text',
+    'views',
+    'node',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Views used by this test.
+   *
+   * @var array
+   */
+  public static $testViews = ['test_field_filters'];
+
+  /**
+   * The vocabulary used for creating terms.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  /**
+   * List of taxonomy term names by language.
+   *
+   * @var array
+   */
+  public $termNames = [];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp($import_test_views = TRUE, $modules = []): void {
+    parent::setUp($import_test_views, $modules);
+
+    // Add two new languages.
+    ConfigurableLanguage::createFromLangcode('fr')->save();
+    ConfigurableLanguage::createFromLangcode('es')->save();
+
+    // Set up term names.
+    $this->termNames = [
+      'en' => 'Food in Paris',
+      'es' => 'Comida en Paris',
+      'fr' => 'Nourriture en Paris',
+    ];
+
+    // Create a vocabulary.
+    $this->vocabulary = Vocabulary::create([
+      'name' => 'Views testing tags',
+      'vid' => 'views_testing_tags',
+    ]);
+    $this->vocabulary->save();
+
+    // Add a translatable field to the vocabulary.
+    $field = FieldStorageConfig::create([
+      'field_name' => 'field_foo',
+      'entity_type' => 'taxonomy_term',
+      'type' => 'text',
+    ]);
+    $field->save();
+    FieldConfig::create([
+      'field_name' => 'field_foo',
+      'entity_type' => 'taxonomy_term',
+      'label' => 'Foo',
+      'bundle' => 'views_testing_tags',
+    ])->save();
+
+    // Create term with translations.
+    $taxonomy = $this->createTermWithProperties(['name' => $this->termNames['en'], 'langcode' => 'en', 'description' => $this->termNames['en'], 'field_foo' => $this->termNames['en']]);
+    foreach (['es', 'fr'] as $langcode) {
+      $translation = $taxonomy->addTranslation($langcode, ['name' => $this->termNames[$langcode]]);
+      $translation->description->value = $this->termNames[$langcode];
+      $translation->field_foo->value = $this->termNames[$langcode];
+    }
+    $taxonomy->save();
+
+    Views::viewsData()->clear();
+
+    ViewTestData::createTestViews(static::class, ['taxonomy_test_views']);
+  }
+
+  /**
+   * Tests description and term name filters.
+   */
+  public function testFilters(): void {
+    // Test the name filter page, which filters for name contains 'Comida'.
+    // Should show just the Spanish translation, once.
+    $this->assertPageCounts('test-name-filter', ['es' => 1, 'fr' => 0, 'en' => 0], 'Comida name filter');
+
+    // Test the description filter page, which filters for description contains
+    // 'Comida'. Should show just the Spanish translation, once.
+    $this->assertPageCounts('test-desc-filter', ['es' => 1, 'fr' => 0, 'en' => 0], 'Comida description filter');
+
+    // Test the field filter page, which filters for field_foo contains
+    // 'Comida'. Should show just the Spanish translation, once.
+    $this->assertPageCounts('test-field-filter', ['es' => 1, 'fr' => 0, 'en' => 0], 'Comida field filter');
+
+    // Test the name Paris filter page, which filters for name contains
+    // 'Paris'. Should show each translation once.
+    $this->assertPageCounts('test-name-paris', ['es' => 1, 'fr' => 1, 'en' => 1], 'Paris name filter');
+
+    // Test the description Paris page, which filters for description contains
+    // 'Paris'. Should show each translation, once.
+    $this->assertPageCounts('test-desc-paris', ['es' => 1, 'fr' => 1, 'en' => 1], 'Paris description filter');
+
+    // Test the field Paris filter page, which filters for field_foo contains
+    // 'Paris'. Should show each translation once.
+    $this->assertPageCounts('test-field-paris', ['es' => 1, 'fr' => 1, 'en' => 1], 'Paris field filter');
+
+  }
+
+  /**
+   * Asserts that the given taxonomy translation counts are correct.
+   *
+   * @param string $path
+   *   Path of the page to test.
+   * @param array $counts
+   *   Array whose keys are languages, and values are the number of times
+   *   that translation should be shown on the given page.
+   * @param string $message
+   *   Message suffix to display.
+   *
+   * @internal
+   */
+  protected function assertPageCounts(string $path, array $counts, string $message): void {
+    // Get the text of the page.
+    $this->drupalGet($path);
+    $text = $this->getTextContent();
+
+    // Check the counts. Note that the title and body are both shown on the
+    // page, and they are the same. So the title/body string should appear on
+    // the page twice as many times as the input count.
+    foreach ($counts as $langcode => $count) {
+      $this->assertEquals(2 * $count, substr_count($text, $this->termNames[$langcode]), 'Translation ' . $langcode . ' has count ' . $count . ' with ' . $message);
+    }
+  }
+
+  /**
+   * Creates a taxonomy term with specified name and other properties.
+   *
+   * @param array $properties
+   *   Array of properties and field values to set.
+   *
+   * @return \Drupal\taxonomy\TermInterface
+   *   The created taxonomy term.
+   */
+  protected function createTermWithProperties($properties) {
+    // Use the first available text format.
+    $filter_formats = filter_formats();
+    $format = array_pop($filter_formats);
+
+    $properties += [
+      'name' => $this->randomMachineName(),
+      'description' => $this->randomMachineName(),
+      'langcode' => LanguageInterface::LANGCODE_NOT_SPECIFIED,
+      'field_foo' => $this->randomMachineName(),
+    ];
+
+    $term = Term::create([
+      'name' => $properties['name'],
+      'description' => $properties['description'],
+      'format' => $format->id(),
+      'vid' => $this->vocabulary->id(),
+      'langcode' => $properties['langcode'],
+    ]);
+    $term->field_foo->value = $properties['field_foo'];
+    $term->save();
+    return $term;
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TaxonomyIndexTidUiTest.php

@@ -0,0 +1,556 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+use Drupal\Tests\field\Traits\EntityReferenceFieldCreationTrait;
+use Drupal\taxonomy\Entity\Term;
+use Drupal\taxonomy\Entity\Vocabulary;
+use Drupal\Tests\views_ui\Functional\UITestBase;
+use Drupal\views\Tests\ViewTestData;
+use Drupal\views\Entity\View;
+
+/**
+ * Tests the taxonomy index filter handler UI.
+ *
+ * @group taxonomy
+ * @group #slow
+ * @see \Drupal\taxonomy\Plugin\views\field\TaxonomyIndexTid
+ */
+class TaxonomyIndexTidUiTest extends UITestBase {
+
+  use EntityReferenceFieldCreationTrait;
+
+  /**
+   * Views used by this test.
+   *
+   * @var array
+   */
+  public static $testViews = [
+    'test_filter_taxonomy_index_tid',
+    'test_taxonomy_term_name',
+    'test_taxonomy_exposed_grouped_filter',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = [
+    'node',
+    'taxonomy',
+    'views',
+    'views_ui',
+    'taxonomy_test_views',
+  ];
+
+  /**
+   * A nested array of \Drupal\taxonomy\TermInterface objects.
+   *
+   * @var \Drupal\taxonomy\TermInterface[][]
+   */
+  protected $terms = [];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp($import_test_views = TRUE, $modules = []): void {
+    parent::setUp($import_test_views, $modules);
+
+    $this->adminUser = $this->drupalCreateUser([
+      'administer taxonomy',
+      'administer views',
+    ]);
+    $this->drupalLogin($this->adminUser);
+
+    Vocabulary::create([
+      'vid' => 'tags',
+      'name' => 'Tags',
+    ])->save();
+
+    // Setup a hierarchy which looks like this:
+    // term 0.0
+    // term 1.0
+    // - term 1.1
+    // term 2.0
+    // - term 2.1
+    // - term 2.2
+    for ($i = 0; $i < 3; $i++) {
+      for ($j = 0; $j <= $i; $j++) {
+        $this->terms[$i][$j] = $term = Term::create([
+          'vid' => 'tags',
+          'name' => "Term $i.$j",
+          'parent' => isset($this->terms[$i][0]) ? $this->terms[$i][0]->id() : 0,
+        ]);
+        $term->save();
+      }
+    }
+    ViewTestData::createTestViews(static::class, ['taxonomy_test_views']);
+
+    // Extra taxonomy and terms.
+    Vocabulary::create([
+      'vid' => 'other_tags',
+      'name' => 'Other tags',
+    ])->save();
+
+    $this->terms[3][0] = $term = Term::create([
+      'vid' => 'tags',
+      'name' => "Term 3.0",
+    ]);
+    $term->save();
+
+    Vocabulary::create([
+      'vid' => 'empty_vocabulary',
+      'name' => 'Empty Vocabulary',
+    ])->save();
+  }
+
+  /**
+   * Tests the filter UI.
+   */
+  public function testFilterUI(): void {
+    $this->drupalGet('admin/structure/views/nojs/handler/test_filter_taxonomy_index_tid/default/filter/tid');
+
+    $result = $this->assertSession()->selectExists('edit-options-value')->findAll('css', 'option');
+
+    // Ensure that the expected hierarchy is available in the UI.
+    $counter = 0;
+    for ($i = 0; $i < 3; $i++) {
+      for ($j = 0; $j <= $i; $j++) {
+        $option = $result[$counter++];
+        $prefix = $this->terms[$i][$j]->parent->target_id ? '-' : '';
+        $tid = $option->getAttribute('value');
+
+        $this->assertEquals($prefix . $this->terms[$i][$j]->getName(), $option->getText());
+        $this->assertEquals($this->terms[$i][$j]->id(), $tid);
+      }
+    }
+
+    // Ensure the autocomplete input element appears when using the 'textfield'
+    // type.
+    $view = View::load('test_filter_taxonomy_index_tid');
+    $display =& $view->getDisplay('default');
+    $display['display_options']['filters']['tid']['type'] = 'textfield';
+    $view->save();
+    $this->drupalGet('admin/structure/views/nojs/handler/test_filter_taxonomy_index_tid/default/filter/tid');
+    $this->assertSession()->fieldExists('edit-options-value');
+
+    // Tests \Drupal\taxonomy\Plugin\views\filter\TaxonomyIndexTid::calculateDependencies().
+    $expected = [
+      'config' => [
+        'taxonomy.vocabulary.tags',
+      ],
+      'content' => [
+        'taxonomy_term:tags:' . Term::load(2)->uuid(),
+      ],
+      'module' => [
+        'node',
+        'taxonomy',
+        'user',
+      ],
+    ];
+    $this->assertSame($expected, $view->calculateDependencies()->getDependencies());
+  }
+
+  /**
+   * Tests exposed taxonomy filters.
+   */
+  public function testExposedFilter(): void {
+    $node_type = $this->drupalCreateContentType(['type' => 'page']);
+
+    // Create the tag field itself.
+    $field_name = 'taxonomy_tags';
+    $this->createEntityReferenceField('node', $node_type->id(), $field_name, NULL, 'taxonomy_term');
+
+    // Create 4 nodes: 1 without a term, 2 with the same term, and 1 with a
+    // different term.
+    $node1 = $this->drupalCreateNode();
+    $node2 = $this->drupalCreateNode([
+      $field_name => [['target_id' => $this->terms[1][0]->id()]],
+    ]);
+    $node3 = $this->drupalCreateNode([
+      $field_name => [['target_id' => $this->terms[1][0]->id()]],
+    ]);
+    $node4 = $this->drupalCreateNode([
+      $field_name => [['target_id' => $this->terms[2][0]->id()]],
+    ]);
+
+    // Only the nodes with the selected term should be shown.
+    $this->drupalGet('test-filter-taxonomy-index-tid');
+    $this->assertSession()->pageTextNotContains($node1->getTitle());
+    $this->assertSession()->linkByHrefNotExists($node1->toUrl()->toString());
+    $xpath_node2_link = $this->assertSession()->buildXPathQuery('//div[@class="views-row"]//a[@href=:url and text()=:label]', [
+      ':url' => $node2->toUrl()->toString(),
+      ':label' => $node2->label(),
+    ]);
+    $this->assertSession()->elementsCount('xpath', $xpath_node2_link, 1);
+    $xpath_node3_link = $this->assertSession()->buildXPathQuery('//div[@class="views-row"]//a[@href=:url and text()=:label]', [
+      ':url' => $node3->toUrl()->toString(),
+      ':label' => $node3->label(),
+    ]);
+    $this->assertSession()->elementsCount('xpath', $xpath_node3_link, 1);
+    $this->assertSession()->pageTextNotContains($node4->getTitle());
+    $this->assertSession()->linkByHrefNotExists($node4->toUrl()->toString());
+
+    // Expose the filter.
+    $this->drupalGet('admin/structure/views/nojs/handler/test_filter_taxonomy_index_tid/default/filter/tid');
+    $this->submitForm([], 'Expose filter');
+    // Set the operator to 'empty' and remove the default term ID.
+    $this->submitForm([
+      'options[operator]' => 'empty',
+      'options[value][]' => [],
+    ], 'Apply');
+    // Save the view.
+    $this->submitForm([], 'Save');
+
+    // After switching to 'empty' operator, the node without a term should be
+    // shown.
+    $this->drupalGet('test-filter-taxonomy-index-tid');
+    $xpath_node1_link = $this->assertSession()->buildXPathQuery('//div[@class="views-row"]//a[@href=:url and text()=:label]', [
+      ':url' => $node1->toUrl()->toString(),
+      ':label' => $node1->label(),
+    ]);
+    $this->assertSession()->elementsCount('xpath', $xpath_node1_link, 1);
+    $this->assertSession()->pageTextNotContains($node2->getTitle());
+    $this->assertSession()->linkByHrefNotExists($node2->toUrl()->toString());
+    $this->assertSession()->pageTextNotContains($node3->getTitle());
+    $this->assertSession()->linkByHrefNotExists($node3->toUrl()->toString());
+    $this->assertSession()->pageTextNotContains($node4->getTitle());
+    $this->assertSession()->linkByHrefNotExists($node4->toUrl()->toString());
+
+    // Set the operator to 'not empty'.
+    $this->drupalGet('admin/structure/views/nojs/handler/test_filter_taxonomy_index_tid/default/filter/tid');
+    $this->submitForm(['options[operator]' => 'not empty'], 'Apply');
+    // Save the view.
+    $this->submitForm([], 'Save');
+
+    // After switching to 'not empty' operator, all nodes with terms should be
+    // shown.
+    $this->drupalGet('test-filter-taxonomy-index-tid');
+    $this->assertSession()->pageTextNotContains($node1->getTitle());
+    $this->assertSession()->linkByHrefNotExists($node1->toUrl()->toString());
+    $xpath_node2_link = $this->assertSession()->buildXPathQuery('//div[@class="views-row"]//a[@href=:url and text()=:label]', [
+      ':url' => $node2->toUrl()->toString(),
+      ':label' => $node2->label(),
+    ]);
+    $this->assertSession()->elementsCount('xpath', $xpath_node2_link, 1);
+    $xpath_node3_link = $this->assertSession()->buildXPathQuery('//div[@class="views-row"]//a[@href=:url and text()=:label]', [
+      ':url' => $node3->toUrl()->toString(),
+      ':label' => $node3->label(),
+    ]);
+    $this->assertSession()->elementsCount('xpath', $xpath_node3_link, 1);
+    $xpath_node4_link = $this->assertSession()->buildXPathQuery('//div[@class="views-row"]//a[@href=:url and text()=:label]', [
+      ':url' => $node4->toUrl()->toString(),
+      ':label' => $node4->label(),
+    ]);
+    $this->assertSession()->elementsCount('xpath', $xpath_node4_link, 1);
+
+    // Select 'Term ID' as the field to be displayed.
+    $edit = ['name[taxonomy_term_field_data.tid]' => TRUE];
+    $this->drupalGet('admin/structure/views/nojs/add-handler/test_taxonomy_term_name/default/field');
+    $this->submitForm($edit, 'Add and configure fields');
+    // Select 'Term' and 'Vocabulary' as filters.
+    $edit = [
+      'name[taxonomy_term_field_data.tid]' => TRUE,
+      'name[taxonomy_term_field_data.vid]' => TRUE,
+    ];
+    $this->drupalGet('admin/structure/views/nojs/add-handler/test_taxonomy_term_name/default/filter');
+    $this->submitForm($edit, 'Add and configure filter criteria');
+    // Select 'Empty Vocabulary' and 'Autocomplete' from the list of options.
+    $this->drupalGet('admin/structure/views/nojs/handler-extra/test_taxonomy_term_name/default/filter/tid');
+    $this->submitForm([], 'Apply and continue');
+    // Expose the filter.
+    $edit = ['options[expose_button][checkbox][checkbox]' => TRUE];
+    $this->drupalGet('admin/structure/views/nojs/handler/test_taxonomy_term_name/default/filter/tid');
+    $this->submitForm($edit, 'Expose filter');
+    $this->drupalGet('admin/structure/views/nojs/handler/test_taxonomy_term_name/default/filter/tid');
+    $this->submitForm($edit, 'Apply');
+    // Filter 'Taxonomy terms' belonging to 'Empty Vocabulary'.
+    $edit = ['options[value][empty_vocabulary]' => TRUE];
+    $this->drupalGet('admin/structure/views/nojs/handler/test_taxonomy_term_name/default/filter/vid');
+    $this->submitForm($edit, 'Apply');
+    $this->drupalGet('admin/structure/views/view/test_taxonomy_term_name/edit/default');
+    $this->submitForm([], 'Save');
+    $this->submitForm([], 'Update preview');
+    $this->assertSession()->pageTextNotContains($node1->getTitle());
+    $this->assertSession()->linkByHrefNotExists($node1->toUrl()->toString());
+    $this->assertSession()->pageTextNotContains($node2->getTitle());
+    $this->assertSession()->linkByHrefNotExists($node2->toUrl()->toString());
+    $this->assertSession()->pageTextNotContains($node3->getTitle());
+    $this->assertSession()->linkByHrefNotExists($node3->toUrl()->toString());
+    $this->assertSession()->pageTextNotContains($node4->getTitle());
+    $this->assertSession()->linkByHrefNotExists($node4->toUrl()->toString());
+    $this->assertSession()->elementNotExists('xpath', "//div[@class='views-row']");
+  }
+
+  /**
+   * Tests exposed grouped taxonomy filters.
+   */
+  public function testExposedGroupedFilter(): void {
+    // Create a content type with a taxonomy field.
+    $this->drupalCreateContentType(['type' => 'article']);
+    $field_name = 'field_views_testing_tags';
+    $this->createEntityReferenceField('node', 'article', $field_name, NULL, 'taxonomy_term');
+
+    $nodes = [];
+    for ($i = 0; $i < 3; $i++) {
+      $node = [];
+      $node['type'] = 'article';
+      $node['field_views_testing_tags'][0]['target_id'] = $this->terms[$i][0]->id();
+      $nodes[] = $this->drupalCreateNode($node);
+    }
+
+    $this->drupalGet('/admin/structure/views/nojs/handler/test_taxonomy_exposed_grouped_filter/page_1/filter/field_views_testing_tags_target_id');
+    $edit = [
+      'options[group_info][group_items][1][value][]' => [$this->terms[0][0]->id(), $this->terms[1][0]->id()],
+      'options[group_info][group_items][2][value][]' => [$this->terms[1][0]->id(), $this->terms[2][0]->id()],
+      'options[group_info][group_items][3][value][]' => [$this->terms[2][0]->id(), $this->terms[0][0]->id()],
+    ];
+    $this->submitForm($edit, 'Apply');
+    $this->submitForm([], 'Save');
+
+    // Visit the view's page URL and validate the results.
+    $this->drupalGet('/test-taxonomy-exposed-grouped-filter');
+    $this->submitForm(['field_views_testing_tags_target_id' => 1], 'Apply');
+    $this->assertSession()->pageTextContains($nodes[0]->getTitle());
+    $this->assertSession()->pageTextContains($nodes[1]->getTitle());
+    $this->assertSession()->pageTextNotContains($nodes[2]->getTitle());
+
+    $this->submitForm(['field_views_testing_tags_target_id' => 2], 'Apply');
+    $this->assertSession()->pageTextContains($nodes[1]->getTitle());
+    $this->assertSession()->pageTextContains($nodes[2]->getTitle());
+    $this->assertSession()->pageTextNotContains($nodes[0]->getTitle());
+
+    $this->submitForm(['field_views_testing_tags_target_id' => 3], 'Apply');
+    $this->assertSession()->pageTextContains($nodes[0]->getTitle());
+    $this->assertSession()->pageTextContains($nodes[2]->getTitle());
+    $this->assertSession()->pageTextNotContains($nodes[1]->getTitle());
+  }
+
+  /**
+   * Tests that an exposed taxonomy filter doesn't show unpublished terms.
+   */
+  public function testExposedUnpublishedFilterOptions(): void {
+    $this->terms[1][0]->setUnpublished()->save();
+    // Expose the filter.
+    $this->drupalGet('admin/structure/views/nojs/handler/test_filter_taxonomy_index_tid/default/filter/tid');
+    $this->submitForm([], 'Expose filter');
+    $edit = ['options[expose_button][checkbox][checkbox]' => TRUE];
+    $this->submitForm($edit, 'Apply');
+    $this->submitForm([], 'Save');
+    // Make sure the unpublished term is shown to the admin user.
+    $this->drupalGet('test-filter-taxonomy-index-tid');
+    $this->assertNotEmpty($this->cssSelect('option[value="' . $this->terms[0][0]->id() . '"]'));
+    $this->assertNotEmpty($this->cssSelect('option[value="' . $this->terms[1][0]->id() . '"]'));
+    $this->drupalLogout();
+    $this->drupalGet('test-filter-taxonomy-index-tid');
+    // Make sure the unpublished term isn't shown to the anonymous user.
+    $this->assertNotEmpty($this->cssSelect('option[value="' . $this->terms[0][0]->id() . '"]'));
+    $this->assertEmpty($this->cssSelect('option[value="' . $this->terms[1][0]->id() . '"]'));
+
+    // Tests that the term also isn't shown when not showing hierarchy.
+    $this->drupalLogin($this->adminUser);
+    $edit = [
+      'options[hierarchy]' => FALSE,
+    ];
+    $this->drupalGet('admin/structure/views/nojs/handler-extra/test_filter_taxonomy_index_tid/default/filter/tid');
+    $this->submitForm($edit, 'Apply');
+    $this->submitForm([], 'Save');
+    $this->drupalGet('test-filter-taxonomy-index-tid');
+    $this->assertNotEmpty($this->cssSelect('option[value="' . $this->terms[0][0]->id() . '"]'));
+    $this->assertNotEmpty($this->cssSelect('option[value="' . $this->terms[1][0]->id() . '"]'));
+    $this->drupalLogout();
+    $this->drupalGet('test-filter-taxonomy-index-tid');
+    // Make sure the unpublished term isn't shown to the anonymous user.
+    $this->assertNotEmpty($this->cssSelect('option[value="' . $this->terms[0][0]->id() . '"]'));
+    $this->assertEmpty($this->cssSelect('option[value="' . $this->terms[1][0]->id() . '"]'));
+  }
+
+  /**
+   * Tests using the TaxonomyIndexTid in a filter group.
+   */
+  public function testFilterGrouping(): void {
+    $node_type = $this->drupalCreateContentType(['type' => 'page']);
+
+    // Create the tag field itself.
+    $field_name = 'taxonomy_tags';
+    $this->createEntityReferenceField('node', $node_type->id(), $field_name, NULL, 'taxonomy_term');
+
+    // Create the other tag field itself.
+    $field_name2 = 'taxonomy_other_tags';
+    $this->createEntityReferenceField('node', $node_type->id(), $field_name2, NULL, 'taxonomy_term');
+
+    // Create 5 nodes: 1 node without any tagging, 2 nodes tagged with 1 term,
+    // 1 node with 2 tagged terms and 1 with other tags term.
+    $node_no_term = $this->drupalCreateNode();
+    $node_with_term_1_0 = $this->drupalCreateNode([
+      $field_name => [['target_id' => $this->terms[1][0]->id()]],
+    ]);
+    $node_with_terms_1_0_and_1_1 = $this->drupalCreateNode([
+      $field_name => [
+        ['target_id' => $this->terms[1][0]->id()],
+        ['target_id' => $this->terms[1][1]->id()],
+      ],
+    ]);
+    $node_with_term_2_0 = $this->drupalCreateNode([
+      $field_name => [['target_id' => $this->terms[2][0]->id()]],
+    ]);
+
+    $node_with_term_3_0 = $this->drupalCreateNode([
+      $field_name2 => [['target_id' => $this->terms[3][0]->id()]],
+    ]);
+
+    // Create two groups. The first group contains the published filter and set
+    // up the second group as an 'OR' group. The first subgroup of the second
+    // filter group will vary as follows:
+    // - multiple values vs single value
+    // - not vs or operator values
+    $view = View::load('test_filter_taxonomy_index_tid');
+    $display =& $view->getDisplay('default');
+    // Case 1:
+    // - filter "tid" with multiple terms as "is none of"
+    // - filter "tid_2" with a single term as "is one of"
+    $display['display_options']['filters']['tid']['value'][0] = $this->terms[1][0]->id();
+    $display['display_options']['filters']['tid']['value'][1] = $this->terms[1][1]->id();
+    $display['display_options']['filters']['tid']['operator'] = 'not';
+    $display['display_options']['filters']['tid']['group'] = 2;
+    $display['display_options']['filters']['tid_2'] = $display['display_options']['filters']['tid'];
+    $display['display_options']['filters']['tid_2']['id'] = 'tid_2';
+    $display['display_options']['filters']['tid_2']['value'][0] = $this->terms[2][0]->id();
+    $display['display_options']['filters']['tid_2']['operator'] = 'or';
+    $display['display_options']['filters']['tid_2']['group'] = 2;
+    $display['display_options']['filter_groups'] = [
+      'operator' => 'AND',
+      'groups' => [
+        1 => 'AND',
+        2 => 'OR',
+      ],
+    ];
+    $view->save();
+
+    $this->drupalGet('test-filter-taxonomy-index-tid');
+    // We expect no nodes tagged with term 1.0 or 1.1. The node tagged with
+    // term 2.0 and the untagged node will be shown.
+    $this->assertSession()->pageTextNotContains($node_with_term_1_0->label());
+    $this->assertSession()->pageTextNotContains($node_with_terms_1_0_and_1_1->label());
+    $this->assertSession()->pageTextContainsOnce($node_with_term_2_0->label());
+    $this->assertSession()->pageTextContainsOnce($node_no_term->label());
+
+    // Case 2:
+    // - filter "tid" with multiple terms as "is one of"
+    // - filter "tid_2" with a single term as "is one of"
+    $view = View::load('test_filter_taxonomy_index_tid');
+    $display =& $view->getDisplay('default');
+    $display['display_options']['filters']['tid']['value'][0] = $this->terms[1][0]->id();
+    $display['display_options']['filters']['tid']['value'][1] = $this->terms[1][1]->id();
+    $display['display_options']['filters']['tid']['operator'] = 'or';
+    $display['display_options']['filters']['tid']['group'] = 2;
+    $display['display_options']['filters']['tid_2'] = $display['display_options']['filters']['tid'];
+    $display['display_options']['filters']['tid_2']['id'] = 'tid_2';
+    $display['display_options']['filters']['tid_2']['value'][0] = $this->terms[2][0]->id();
+    $display['display_options']['filters']['tid_2']['operator'] = 'or';
+    $display['display_options']['filters']['tid_2']['group'] = 2;
+    $view->save();
+
+    $this->drupalGet('test-filter-taxonomy-index-tid');
+    // We expect all the tagged nodes but not the untagged node.
+    $this->assertSession()->pageTextContainsOnce($node_with_term_1_0->label());
+    // The view does not have DISTINCT query enabled, the node tagged with
+    // both 1.0 and 1.1 will appear twice.
+    $this->assertSession()->pageTextMatchesCount(2, "/{$node_with_terms_1_0_and_1_1->label()}/");
+    $this->assertSession()->pageTextContainsOnce($node_with_term_2_0->label());
+    $this->assertSession()->pageTextNotContains($node_no_term->label());
+
+    // Case 3:
+    // - filter "tid" with a single term as "is none of"
+    // - filter "tid_2" with a single term as "is one of"
+    $view = View::load('test_filter_taxonomy_index_tid');
+    $display =& $view->getDisplay('default');
+    $display['display_options']['filters']['tid']['value'] = [];
+    $display['display_options']['filters']['tid']['value'][0] = $this->terms[1][0]->id();
+    $display['display_options']['filters']['tid']['operator'] = 'not';
+    $display['display_options']['filters']['tid']['group'] = 2;
+    $display['display_options']['filters']['tid_2'] = $display['display_options']['filters']['tid'];
+    $display['display_options']['filters']['tid_2']['id'] = 'tid_2';
+    $display['display_options']['filters']['tid_2']['value'][0] = $this->terms[2][0]->id();
+    $display['display_options']['filters']['tid_2']['operator'] = 'or';
+    $display['display_options']['filters']['tid_2']['group'] = 2;
+    $view->save();
+
+    $this->drupalGet('test-filter-taxonomy-index-tid');
+    // We expect none of the nodes tagged with term 1.0. The node tagged with
+    // term 2.0 and the untagged node should be shown.
+    $this->assertSession()->pageTextNotContains($node_with_term_1_0->label());
+    $this->assertSession()->pageTextNotContains($node_with_terms_1_0_and_1_1->label());
+    $this->assertSession()->pageTextContainsOnce($node_with_term_2_0->label());
+    $this->assertSession()->pageTextContainsOnce($node_no_term->label());
+
+    // Case 4:
+    // - filter "tid" with a single term as "is one of"
+    // - filter "tid_2" with a single term as "is one of"
+    $view = View::load('test_filter_taxonomy_index_tid');
+    $display =& $view->getDisplay('default');
+    $display['display_options']['filters']['tid']['value'] = [];
+    $display['display_options']['filters']['tid']['value'][0] = $this->terms[1][0]->id();
+    $display['display_options']['filters']['tid']['operator'] = 'or';
+    $display['display_options']['filters']['tid']['group'] = 2;
+    $display['display_options']['filters']['tid_2'] = $display['display_options']['filters']['tid'];
+    $display['display_options']['filters']['tid_2']['id'] = 'tid_2';
+    $display['display_options']['filters']['tid_2']['value'][0] = $this->terms[2][0]->id();
+    $view->save();
+
+    $this->drupalGet('test-filter-taxonomy-index-tid');
+    // We expect all the tagged nodes to be shown but not the untagged node.
+    $this->assertSession()->pageTextContainsOnce($node_with_term_1_0->label());
+    $this->assertSession()->pageTextContainsOnce($node_with_terms_1_0_and_1_1->label());
+    $this->assertSession()->pageTextContainsOnce($node_with_term_2_0->label());
+    $this->assertSession()->pageTextNotContains($node_no_term->label());
+
+    // Different fields/taxonomies filters/values.
+    // Case 5: OR
+    // - filter "tid" with terms from tags as "is one of"
+    // - filter "taxonomy_other_tags_target_id" with term from other tags
+    // as "is one of".
+    $view = View::load('test_filter_taxonomy_index_tid');
+    $display = &$view->getDisplay('default');
+    $display['display_options']['filters']['tid']['value'][0] = $this->terms[1][0]->id();
+    $display['display_options']['filters']['tid']['value'][1] = $this->terms[1][1]->id();
+    $display['display_options']['filters']['tid']['operator'] = 'or';
+    $display['display_options']['filters']['tid']['group'] = 2;
+    $display['display_options']['filters']['taxonomy_other_tags_target_id'] = $display['display_options']['filters']['tid'];
+    $display['display_options']['filters']['taxonomy_other_tags_target_id']['id'] = 'taxonomy_other_tags_target_id';
+    $display['display_options']['filters']['taxonomy_other_tags_target_id']['value'][0] = $this->terms[3][0]->id();
+    $display['display_options']['filters']['taxonomy_other_tags_target_id']['operator'] = 'or';
+    $display['display_options']['filters']['taxonomy_other_tags_target_id']['group'] = 2;
+    $display['display_options']['filters']['taxonomy_other_tags_target_id']['table'] = 'node__taxonomy_other_tags';
+    $display['display_options']['filters']['taxonomy_other_tags_target_id']['field'] = 'taxonomy_other_tags_target_id';
+    unset($display['display_options']['filters']['tid_2']);
+    $display['display_options']['filter_groups'] = [
+      'operator' => 'AND',
+      'groups' => [
+        1 => 'AND',
+        2 => 'OR',
+      ],
+    ];
+    $view->save();
+
+    $this->drupalGet('test-filter-taxonomy-index-tid');
+    // We expect no nodes tagged with term 1.0 or 1.1. The node tagged with
+    // term 3.0 and the untagged node will be shown.
+    $this->assertSession()->pageTextContainsOnce($node_with_term_1_0->label());
+    // The view does not have DISTINCT query enabled, the node tagged with
+    // both 1.0 and 1.1 will appear twice.
+    $this->assertSession()->pageTextMatchesCount(2, "/{$node_with_terms_1_0_and_1_1->label()}/");
+    $this->assertSession()->pageTextContainsOnce($node_with_term_3_0->label());
+    $this->assertSession()->pageTextNotContains($node_with_term_2_0->label());
+    $this->assertSession()->pageTextNotContains($node_no_term->label());
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TaxonomyParentUITest.php

@@ -0,0 +1,51 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+use Drupal\Tests\views_ui\Functional\UITestBase;
+
+/**
+ * Tests views taxonomy parent plugin UI.
+ *
+ * @group taxonomy
+ * @see Drupal\taxonomy\Plugin\views\access\Role
+ */
+class TaxonomyParentUITest extends UITestBase {
+
+  /**
+   * Views used by this test.
+   *
+   * @var array
+   */
+  public static $testViews = ['test_taxonomy_parent'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['taxonomy', 'taxonomy_test_views'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp($import_test_views = TRUE, $modules = ['taxonomy_test_views']): void {
+    parent::setUp($import_test_views, $modules);
+  }
+
+  /**
+   * Tests the taxonomy parent plugin UI.
+   */
+  public function testTaxonomyParentUI(): void {
+    $this->drupalGet('admin/structure/views/nojs/handler/test_taxonomy_parent/default/relationship/parent');
+    $this->assertSession()->pageTextNotContains('The handler for this item is broken or missing.');
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TaxonomyRelationshipTest.php

@@ -0,0 +1,119 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+use Drupal\node\NodeInterface;
+use Drupal\taxonomy\TermInterface;
+use Drupal\views\Views;
+
+/**
+ * Tests taxonomy relationships with parent term and node.
+ *
+ * @group taxonomy
+ */
+class TaxonomyRelationshipTest extends TaxonomyTestBase {
+
+  /**
+   * Stores the terms used in the tests.
+   *
+   * @var \Drupal\taxonomy\TermInterface[]
+   */
+  protected $terms = [];
+
+  /**
+   * Views used by this test.
+   *
+   * @var array
+   */
+  public static $testViews = ['test_taxonomy_term_relationship'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp($import_test_views = TRUE, $modules = []): void {
+    parent::setUp($import_test_views, $modules);
+
+    // Make term2 parent of term1.
+    $this->term1->set('parent', $this->term2->id());
+    $this->term1->save();
+    // Store terms in an array for testing.
+    $this->terms[] = $this->term1;
+    $this->terms[] = $this->term2;
+    // Only set term1 on node1 and term2 on node2 for testing.
+    unset($this->nodes[0]->field_views_testing_tags[1]);
+    $this->nodes[0]->save();
+    unset($this->nodes[1]->field_views_testing_tags[0]);
+    $this->nodes[1]->save();
+
+    Views::viewsData()->clear();
+
+  }
+
+  /**
+   * Tests the taxonomy parent plugin UI.
+   */
+  public function testTaxonomyRelationships(): void {
+
+    // Check the generated views data of taxonomy_index.
+    $views_data = Views::viewsData()->get('taxonomy_index');
+    // Check the table join data.
+    $this->assertEquals('tid', $views_data['table']['join']['taxonomy_term_field_data']['left_field']);
+    $this->assertEquals('tid', $views_data['table']['join']['taxonomy_term_field_data']['field']);
+    $this->assertEquals('nid', $views_data['table']['join']['node_field_data']['left_field']);
+    $this->assertEquals('nid', $views_data['table']['join']['node_field_data']['field']);
+    $this->assertEquals('entity_id', $views_data['table']['join']['taxonomy_term__parent']['left_field']);
+    $this->assertEquals('tid', $views_data['table']['join']['taxonomy_term__parent']['field']);
+
+    // Check the generated views data of taxonomy_term__parent.
+    $views_data = Views::viewsData()->get('taxonomy_term__parent');
+    // Check the table join data.
+    $this->assertEquals('entity_id', $views_data['table']['join']['taxonomy_term__parent']['left_field']);
+    $this->assertEquals('parent_target_id', $views_data['table']['join']['taxonomy_term__parent']['field']);
+    $this->assertEquals('tid', $views_data['table']['join']['taxonomy_term_field_data']['left_field']);
+    $this->assertEquals('entity_id', $views_data['table']['join']['taxonomy_term_field_data']['field']);
+    // Check the parent relationship data.
+    $this->assertEquals('taxonomy_term_field_data', $views_data['parent_target_id']['relationship']['base']);
+    $this->assertEquals('tid', $views_data['parent_target_id']['relationship']['base field']);
+    $this->assertEquals('Parent', $views_data['parent_target_id']['relationship']['label']);
+    $this->assertEquals('standard', $views_data['parent_target_id']['relationship']['id']);
+    // Check the parent filter and argument data.
+    $this->assertEquals('numeric', $views_data['parent_target_id']['filter']['id']);
+    $this->assertEquals('taxonomy', $views_data['parent_target_id']['argument']['id']);
+
+    // Check an actual test view.
+    $view = Views::getView('test_taxonomy_term_relationship');
+    $this->executeView($view);
+    /** @var \Drupal\views\ResultRow $row */
+    foreach ($view->result as $index => $row) {
+      // Check that the actual ID of the entity is the expected one.
+      $this->assertEquals($this->terms[$index]->id(), $row->tid);
+
+      // Also check that we have the correct result entity.
+      $this->assertEquals($this->terms[$index]->id(), $row->_entity->id());
+      $this->assertInstanceOf(TermInterface::class, $row->_entity);
+
+      if (!$index) {
+        $this->assertInstanceOf(TermInterface::class, $row->_relationship_entities['parent']);
+        $this->assertEquals($this->term2->id(), $row->_relationship_entities['parent']->id());
+        $this->assertEquals($this->term2->id(), $row->taxonomy_term_field_data_taxonomy_term__parent_tid);
+      }
+      $this->assertInstanceOf(NodeInterface::class, $row->_relationship_entities['nid']);
+      $this->assertEquals($this->nodes[$index]->id(), $row->_relationship_entities['nid']->id());
+    }
+
+    // Test node fields are available through relationship.
+    \Drupal::service('module_installer')->install(['views_ui']);
+    $this->drupalLogin($this->createUser(['administer views']));
+    $this->drupalGet('admin/structure/views/view/test_taxonomy_term_relationship');
+    $this->click('#views-add-field');
+    $this->assertSession()->pageTextContains('Body');
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermArgumentDepthTest.php

@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+/**
+ * Tests the taxonomy term with depth argument.
+ *
+ * @group taxonomy
+ */
+class TaxonomyTermArgumentDepthTest extends TaxonomyTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'taxonomy',
+    'taxonomy_test_views',
+    'views',
+    'node',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $testViews = ['test_argument_taxonomy_index_tid_depth'];
+
+  /**
+   * @var \Drupal\taxonomy\TermInterface[]
+   */
+  protected $terms = [];
+
+  /**
+   * @var \Drupal\views\ViewExecutable
+   */
+  protected $view;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp($import_test_views = TRUE, $modules = []): void {
+    parent::setUp($import_test_views, $modules);
+
+    // Create a term with markup in the label.
+    $first = $this->createTerm(['name' => '<em>First</em>']);
+
+    // Create a node w/o any terms.
+    $settings = ['type' => 'article'];
+
+    // Create a node with linked to the term.
+    $settings['field_views_testing_tags'][0]['target_id'] = $first->id();
+    $this->nodes[] = $this->drupalCreateNode($settings);
+
+    $this->terms[0] = $first;
+  }
+
+  /**
+   * Tests title escaping.
+   */
+  public function testTermWithDepthArgumentTitleEscaping(): void {
+    $this->drupalGet('test_argument_taxonomy_index_tid_depth/' . $this->terms[0]->id());
+    $this->assertSession()->assertEscaped($this->terms[0]->label());
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermViewTest.php

@@ -0,0 +1,171 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\language\Entity\ConfigurableLanguage;
+use Drupal\node\Entity\Node;
+use Drupal\user\Entity\Role;
+use Drupal\user\RoleInterface;
+use Drupal\views\Views;
+
+/**
+ * Tests the taxonomy term view page and its translation.
+ *
+ * @group taxonomy
+ */
+class TaxonomyTermViewTest extends TaxonomyTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['taxonomy', 'views'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * A user with permissions to administer taxonomy.
+   *
+   * @var \Drupal\user\UserInterface
+   */
+  protected $adminUser;
+
+  /**
+   * Name of the taxonomy term reference field.
+   *
+   * @var string
+   */
+  protected $fieldName1;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp($import_test_views = TRUE, $modules = []): void {
+    parent::setUp($import_test_views, $modules);
+
+    // Create an administrative user.
+    $this->adminUser = $this->drupalCreateUser([
+      'administer taxonomy',
+      'bypass node access',
+    ]);
+    $this->drupalLogin($this->adminUser);
+
+    // Create a vocabulary and add two term reference fields to article nodes.
+
+    $this->fieldName1 = $this->randomMachineName();
+
+    $handler_settings = [
+      'target_bundles' => [
+        $this->vocabulary->id() => $this->vocabulary->id(),
+      ],
+      'auto_create' => TRUE,
+    ];
+    $this->createEntityReferenceField('node', 'article', $this->fieldName1, NULL, 'taxonomy_term', 'default', $handler_settings, FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED);
+
+    /** @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface $display_repository */
+    $display_repository = \Drupal::service('entity_display.repository');
+    $display_repository->getFormDisplay('node', 'article')
+      ->setComponent($this->fieldName1, [
+        'type' => 'options_select',
+      ])
+      ->save();
+    $display_repository->getViewDisplay('node', 'article')
+      ->setComponent($this->fieldName1, [
+        'type' => 'entity_reference_label',
+      ])
+      ->save();
+  }
+
+  /**
+   * Tests that the taxonomy term view is working properly.
+   */
+  public function testTaxonomyTermView(): void {
+    // Create terms in the vocabulary.
+    $term = $this->createTerm();
+
+    // Post an article.
+    $edit = [];
+    $edit['title[0][value]'] = $original_title = $this->randomMachineName();
+    $edit['body[0][value]'] = $this->randomMachineName();
+    $edit["{$this->fieldName1}[]"] = $term->id();
+    $this->drupalGet('node/add/article');
+    $this->submitForm($edit, 'Save');
+    $node = $this->drupalGetNodeByTitle($edit['title[0][value]']);
+
+    $this->drupalGet('taxonomy/term/' . $term->id());
+    $this->assertSession()->pageTextContains($term->label());
+    $this->assertSession()->pageTextContains($node->label());
+
+    \Drupal::service('module_installer')->install(['language', 'content_translation']);
+    ConfigurableLanguage::createFromLangcode('ur')->save();
+    // Enable translation for the article content type and ensure the change is
+    // picked up.
+    \Drupal::service('content_translation.manager')->setEnabled('node', 'article', TRUE);
+    $roles = $this->adminUser->getRoles(TRUE);
+    Role::load(reset($roles))
+      ->grantPermission('create content translations')
+      ->grantPermission('translate any entity')
+      ->save();
+
+    $edit['title[0][value]'] = $translated_title = $this->randomMachineName();
+
+    $this->drupalGet('node/' . $node->id() . '/translations/add/en/ur');
+    $this->submitForm($edit, 'Save (this translation)');
+
+    $this->drupalGet('taxonomy/term/' . $term->id());
+    $this->assertSession()->pageTextContains($term->label());
+    $this->assertSession()->pageTextContains($original_title);
+    $this->assertSession()->pageTextNotContains($translated_title);
+
+    $this->drupalGet('ur/taxonomy/term/' . $term->id());
+    $this->assertSession()->pageTextContains($term->label());
+    $this->assertSession()->pageTextNotContains($original_title);
+    $this->assertSession()->pageTextContains($translated_title);
+
+    // Uninstall language module and ensure that the language is not part of the
+    // query anymore.
+    // @see \Drupal\views\Plugin\views\filter\LanguageFilter::query()
+    $node->delete();
+
+    // We also have to remove the nodes created by the parent ::setUp() method
+    // if we want to be able to uninstall the Content Translation module.
+    foreach (Node::loadMultiple() as $node) {
+      $node->delete();
+    }
+    \Drupal::service('module_installer')->uninstall(['content_translation', 'language']);
+
+    $view = Views::getView('taxonomy_term');
+    $view->initDisplay();
+    $view->setArguments([$term->id()]);
+    $view->build();
+    /** @var \Drupal\Core\Database\Query\Select $query */
+    $query = $view->build_info['query'];
+    $tables = $query->getTables();
+
+    // Ensure that the join to node_field_data is not added by default.
+    $this->assertEquals(['node_field_data', 'taxonomy_index'], array_keys($tables));
+    // Ensure that the filter to the language column is not there by default.
+    $condition = $query->conditions();
+    // We only want to check the no. of conditions in the query.
+    unset($condition['#conjunction']);
+    $this->assertCount(1, $condition);
+
+    // Clear permissions for anonymous users to check access for default views.
+    Role::load(RoleInterface::ANONYMOUS_ID)->revokePermission('access content')->save();
+
+    // Test the default views disclose no data by default.
+    $this->drupalLogout();
+    $this->drupalGet('taxonomy/term/' . $term->id());
+    $this->assertSession()->statusCodeEquals(403);
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/feed');
+    $this->assertSession()->statusCodeEquals(403);
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTestBase.php

@@ -0,0 +1,166 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\Core\Language\LanguageInterface;
+use Drupal\Tests\field\Traits\EntityReferenceFieldCreationTrait;
+use Drupal\Tests\views\Functional\ViewTestBase;
+use Drupal\taxonomy\Entity\Vocabulary;
+use Drupal\taxonomy\Entity\Term;
+use Drupal\views\Tests\ViewTestData;
+
+/**
+ * Base class for all taxonomy tests.
+ */
+abstract class TaxonomyTestBase extends ViewTestBase {
+
+  use EntityReferenceFieldCreationTrait;
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['taxonomy', 'taxonomy_test_views'];
+
+  /**
+   * Stores the nodes used for the different tests.
+   *
+   * @var \Drupal\node\NodeInterface[]
+   */
+  protected $nodes = [];
+
+  /**
+   * The vocabulary used for creating terms.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  /**
+   * Stores the first term used in the different tests.
+   *
+   * @var \Drupal\taxonomy\TermInterface
+   */
+  protected $term1;
+
+  /**
+   * Stores the second term used in the different tests.
+   *
+   * @var \Drupal\taxonomy\TermInterface
+   */
+  protected $term2;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp($import_test_views = TRUE, $modules = []): void {
+    // Important: taxonomy_test_views module must not be in the $modules to
+    // avoid an issue that particular view is already exists.
+    parent::setUp($import_test_views, $modules);
+    $this->mockStandardInstall();
+
+    // This needs to be done again after ::mockStandardInstall() to make
+    // test vocabularies available.
+    // Explicitly add taxonomy_test_views to $modules now, so required views are
+    // being created.
+    $modules[] = 'taxonomy_test_views';
+    if ($import_test_views) {
+      ViewTestData::createTestViews(static::class, $modules);
+    }
+
+    $this->term1 = $this->createTerm();
+    $this->term2 = $this->createTerm();
+
+    $node = [];
+    $node['type'] = 'article';
+    $node['field_views_testing_tags'][]['target_id'] = $this->term1->id();
+    $node['field_views_testing_tags'][]['target_id'] = $this->term2->id();
+    $this->nodes[] = $this->drupalCreateNode($node);
+    $this->nodes[] = $this->drupalCreateNode($node);
+  }
+
+  /**
+   * Provides a workaround for the inability to use the standard profile.
+   *
+   * @see https://www.drupal.org/node/1708692
+   */
+  protected function mockStandardInstall() {
+    $this->drupalCreateContentType([
+      'type' => 'article',
+    ]);
+    // Create the vocabulary for the tag field.
+    $this->vocabulary = Vocabulary::create([
+      'name' => 'Views testing tags',
+      'vid' => 'views_testing_tags',
+    ]);
+    $this->vocabulary->save();
+    $field_name = 'field_' . $this->vocabulary->id();
+
+    $handler_settings = [
+      'target_bundles' => [
+        $this->vocabulary->id() => $this->vocabulary->id(),
+      ],
+      'auto_create' => TRUE,
+    ];
+    $this->createEntityReferenceField('node', 'article', $field_name, 'Tags', 'taxonomy_term', 'default', $handler_settings, FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED);
+
+    /** @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface $display_repository */
+    $display_repository = \Drupal::service('entity_display.repository');
+    $display_repository->getFormDisplay('node', 'article')
+      ->setComponent($field_name, [
+        'type' => 'entity_reference_autocomplete_tags',
+        'weight' => -4,
+      ])
+      ->save();
+
+    $display_repository->getViewDisplay('node', 'article')
+      ->setComponent($field_name, [
+        'type' => 'entity_reference_label',
+        'weight' => 10,
+      ])
+      ->save();
+    $display_repository->getViewDisplay('node', 'article', 'teaser')
+      ->setComponent($field_name, [
+        'type' => 'entity_reference_label',
+        'weight' => 10,
+      ])
+      ->save();
+  }
+
+  /**
+   * Creates and returns a taxonomy term.
+   *
+   * @param array $settings
+   *   (optional) An array of values to override the following default
+   *   properties of the term:
+   *   - name: A random string.
+   *   - description: A random string.
+   *   - format: First available text format.
+   *   - vid: Vocabulary ID of self::$vocabulary object.
+   *   - langcode: LANGCODE_NOT_SPECIFIED.
+   *   Defaults to an empty array.
+   *
+   * @return \Drupal\taxonomy\Entity\Term
+   *   The created taxonomy term.
+   */
+  protected function createTerm(array $settings = []) {
+    $filter_formats = filter_formats();
+    $format = array_pop($filter_formats);
+    $settings += [
+      'name' => $this->randomMachineName(),
+      'description' => $this->randomMachineName(),
+      // Use the first available text format.
+      'format' => $format->id(),
+      'vid' => $this->vocabulary->id(),
+      'langcode' => LanguageInterface::LANGCODE_NOT_SPECIFIED,
+    ];
+    $term = Term::create($settings);
+    $term->save();
+    return $term;
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TaxonomyVocabularyArgumentTest.php

@@ -0,0 +1,83 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+use Drupal\taxonomy\Entity\Vocabulary;
+
+/**
+ * Tests the vocabulary argument.
+ *
+ * @group taxonomy
+ */
+class TaxonomyVocabularyArgumentTest extends TaxonomyTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['taxonomy', 'taxonomy_test_views', 'views'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $testViews = ['test_argument_taxonomy_vocabulary'];
+
+  /**
+   * @var \Drupal\taxonomy\TermInterface[]
+   */
+  protected $terms = [];
+
+  /**
+   * Vocabularies used for creating terms.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface[]
+   */
+  protected $vocabularies;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp($import_test_views = TRUE, $modules = []): void {
+    parent::setUp($import_test_views, $modules);
+
+    // Add default vocabulary to list of vocabularies.
+    $this->vocabularies[] = $this->vocabulary;
+    // Create additional vocabulary.
+    $vocabulary = Vocabulary::create([
+      'name' => 'Views testing category',
+      'vid' => 'views_testing_category',
+    ]);
+    $vocabulary->save();
+    $this->vocabularies[] = $vocabulary;
+
+    // Create some terms.
+    $this->terms[0] = $this->createTerm([
+      'name' => 'First',
+      'vid' => $this->vocabularies[0]->id(),
+    ]);
+    $this->terms[1] = $this->createTerm([
+      'name' => 'Second',
+      'vid' => $this->vocabularies[1]->id(),
+    ]);
+  }
+
+  /**
+   * Tests the vocabulary argument handler.
+   *
+   * @see Drupal\taxonomy\Plugin\views\argument\VocabularyVid
+   */
+  public function testTermWithVocabularyArgument(): void {
+    $this->drupalGet('test_argument_taxonomy_vocabulary/' . $this->vocabularies[0]->id());
+    // First term should be present.
+    $this->assertSession()->pageTextContains($this->terms[0]->label());
+    // Second term should not be present.
+    $this->assertSession()->pageTextNotContains($this->terms[1]->label());
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TermDisplayConfigurableTest.php

@@ -0,0 +1,95 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+/**
+ * Tests making taxonomy term base fields' displays configurable.
+ *
+ * @group taxonomy
+ */
+class TermDisplayConfigurableTest extends TaxonomyTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Views used by this test.
+   *
+   * @var array
+   */
+  public static $testViews = ['test_term_show_entity'];
+
+  /**
+   * Sets base fields to configurable display and check settings are respected.
+   */
+  public function testDisplayConfigurable(): void {
+    $user = $this->drupalCreateUser(['administer nodes']);
+    $this->drupalLogin($user);
+
+    $assert = $this->assertSession();
+
+    // Check the taxonomy_term with default non-configurable display.
+    $this->drupalGet('test_term_show_entity');
+    // Name should be linked to entity and description should be displayed.
+    $assert->pageTextContains($this->term1->getName());
+    $assert->linkByHrefExists($this->term1->toUrl()->toString());
+    $assert->pageTextContains($this->term1->getDescription());
+    $assert->pageTextContains($this->term2->getName());
+    $assert->linkByHrefExists($this->term2->toUrl()->toString());
+    $assert->pageTextContains($this->term2->getDescription());
+    // The field labels should not be present.
+    $assert->pageTextNotContains('Name');
+    $assert->pageTextNotContains('Description');
+
+    // Enable helper module to make base fields' displays configurable.
+    \Drupal::service('module_installer')->install(['taxonomy_term_display_configurable_test']);
+
+    // Configure display.
+    $display = \Drupal::service('entity_display.repository')->getViewDisplay('taxonomy_term', $this->vocabulary->id(), 'default');
+    $display->setComponent('name', [
+      'type' => 'text_default',
+      'label' => 'above',
+    ])->save();
+
+    // Recheck the taxonomy_term with configurable display.
+    $this->drupalGet('test_term_show_entity');
+    // The description should be the first field in each row, with no label.
+    // Name field should be the second field in view row. Value should be
+    // displayed after the label. It should not be linked to the term.
+    $assert->pageTextContains('Name');
+    $assert->pageTextNotContains('Description');
+    $assert->pageTextContains($this->term1->getName());
+    $assert->linkByHrefNotExists($this->term1->toUrl()->toString());
+    $assert->pageTextContains($this->term1->getDescription());
+    $assert->elementTextContains('xpath', '//*[@class="views-row"][1]/div/div[1]//p', $this->term1->getDescription());
+    $assert->elementTextContains('xpath', '//*[@class="views-row"][1]/div/div[2]/div[1]', 'Name');
+    $assert->elementTextContains('xpath', '//*[@class="views-row"][1]/div/div[2]/div[2]', $this->term1->getName());
+    $assert->pageTextContains($this->term2->getName());
+    $assert->linkByHrefNotExists($this->term2->toUrl()->toString());
+    $assert->pageTextContains($this->term2->getDescription());
+    $assert->elementTextContains('xpath', '//*[@class="views-row"][2]/div/div[1]//p', $this->term2->getDescription());
+    $assert->elementTextContains('xpath', '//*[@class="views-row"][2]/div/div[2]/div[1]', 'Name');
+    $assert->elementTextContains('xpath', '//*[@class="views-row"][2]/div/div[2]/div[2]', $this->term2->getName());
+
+    // Remove 'name' field from display.
+    $display->removeComponent('name')->save();
+
+    // Recheck the taxonomy_term with 'name' field removed from display.
+    // There should just be an unlabelled description. Nothing should be
+    // linked to the terms.
+    $this->drupalGet('test_term_show_entity');
+    $assert->pageTextNotContains('Name');
+    $assert->pageTextNotContains('Description');
+    $assert->pageTextNotContains($this->term1->getName());
+    $assert->linkByHrefNotExists($this->term1->toUrl()->toString());
+    $assert->pageTextContains($this->term1->getDescription());
+    $assert->pageTextNotContains($this->term2->getName());
+    $assert->linkByHrefNotExists($this->term2->toUrl()->toString());
+    $assert->pageTextContains($this->term2->getDescription());
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TermNameFieldTest.php

@@ -0,0 +1,69 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+use Drupal\Core\Link;
+use Drupal\views\Views;
+
+/**
+ * Tests the term_name field handler.
+ *
+ * @group taxonomy
+ *
+ * @see \Drupal\taxonomy\Plugin\views\field\TermName
+ */
+class TermNameFieldTest extends TaxonomyTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $testViews = ['test_taxonomy_term_name'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Tests term name field plugin functionality.
+   */
+  public function testTermNameField(): void {
+    $this->term1->name->value = $this->randomMachineName() . ' ' . $this->randomMachineName();
+    $this->term1->save();
+
+    $user = $this->drupalCreateUser(['access content']);
+    $this->drupalLogin($user);
+
+    $view = Views::getView('test_taxonomy_term_name');
+    $view->initDisplay();
+    $this->executeView($view);
+
+    $this->assertEquals($this->term1->getName(), $view->getStyle()->getField(0, 'name'));
+    $this->assertEquals($this->term2->getName(), $view->getStyle()->getField(1, 'name'));
+
+    $view = Views::getView('test_taxonomy_term_name');
+    $display =& $view->storage->getDisplay('default');
+    $display['display_options']['fields']['name']['convert_spaces'] = TRUE;
+    $view->storage->invalidateCaches();
+    $this->executeView($view);
+
+    $this->assertEquals(str_replace(' ', '-', $this->term1->getName()), $view->getStyle()->getField(0, 'name'));
+    $this->assertEquals($this->term2->getName(), $view->getStyle()->getField(1, 'name'));
+
+    // Enable link_to_entity option and ensure that title is displayed properly.
+    $view = Views::getView('test_taxonomy_term_name');
+    $display =& $view->storage->getDisplay('default');
+    $display['display_options']['fields']['name']['convert_spaces'] = TRUE;
+    $display['display_options']['fields']['name']['settings']['link_to_entity'] = TRUE;
+    $view->storage->invalidateCaches();
+    $this->executeView($view);
+
+    $expected_link1 = Link::fromTextAndUrl(str_replace(' ', '-', $this->term1->getName()), $this->term1->toUrl());
+    $expected_link2 = Link::fromTextAndUrl($this->term2->getName(), $this->term2->toUrl());
+    $this->assertEquals($expected_link1->toString(), $view->getStyle()->getField(0, 'name'));
+    $this->assertEquals($expected_link2->toString(), $view->getStyle()->getField(1, 'name'));
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/Views/TermTranslationViewsTest.php

@@ -0,0 +1,132 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional\Views;
+
+use Drupal\Core\Url;
+use Drupal\Tests\taxonomy\Functional\TaxonomyTranslationTestTrait;
+
+/**
+ * Tests for views translation.
+ *
+ * @group taxonomy
+ */
+class TermTranslationViewsTest extends TaxonomyTestBase {
+
+  use TaxonomyTranslationTestTrait;
+
+  /**
+   * Term to translated term mapping.
+   *
+   * @var array
+   */
+  protected $termTranslationMap = [
+    'one' => 'translatedOne',
+    'two' => 'translatedTwo',
+    'three' => 'translatedThree',
+  ];
+
+  /**
+   * Created terms.
+   *
+   * @var \Drupal\taxonomy\Entity\Term[]
+   */
+  protected $terms = [];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['taxonomy', 'language', 'content_translation', 'views'];
+
+  /**
+   * Views used by this test.
+   *
+   * @var array
+   */
+  public static $testViews = ['taxonomy_translated_term_name_test'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Language object.
+   *
+   * @var \Drupal\Core\Language\LanguageInterface|null
+   */
+  protected $translationLanguage;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp($import_test_views = TRUE, $modules = []): void {
+    parent::setUp($import_test_views, $modules);
+    $this->setupLanguages();
+    $this->enableTranslation();
+    $this->setUpTerms();
+    $this->translationLanguage = \Drupal::languageManager()->getLanguage($this->translateToLangcode);
+  }
+
+  /**
+   * Ensure that proper translation is returned when contextual filter.
+   *
+   * Taxonomy term: Term ID & Content: Has taxonomy term ID (with depth)
+   * contextual filters are enabled for two separate view modes.
+   */
+  public function testTermsTranslationWithContextualFilter(): void {
+    $this->drupalLogin($this->rootUser);
+
+    foreach ($this->terms as $term) {
+      // Test with "Content: Has taxonomy term ID (with depth)" contextual filter.
+      // Generate base language url and send request.
+      $url = Url::fromRoute('view.taxonomy_translated_term_name_test.page_1', ['arg_0' => $term->id()])->toString();
+      $this->drupalGet($url);
+      $this->assertSession()->pageTextContains($term->label());
+
+      // Generate translation URL and send request.
+      $url = Url::fromRoute('view.taxonomy_translated_term_name_test.page_1', ['arg_0' => $term->id()], ['language' => $this->translationLanguage])->toString();
+      $this->drupalGet($url);
+      $this->assertSession()->pageTextContains($this->termTranslationMap[$term->label()]);
+
+      // Test with "Taxonomy term: Term ID" contextual filter.
+      // Generate base language url and send request.
+      $url = Url::fromRoute('view.taxonomy_translated_term_name_test.page_2', ['arg_0' => $term->id()])->toString();
+      $this->drupalGet($url);
+      $this->assertSession()->pageTextContains($term->label());
+
+      // Generate translation URL and send request.
+      $url = Url::fromRoute('view.taxonomy_translated_term_name_test.page_2', ['arg_0' => $term->id()], ['language' => $this->translationLanguage])->toString();
+      $this->drupalGet($url);
+      $this->assertSession()->pageTextContains($this->termTranslationMap[$term->label()]);
+    }
+  }
+
+  /**
+   * Setup translated terms in a hierarchy.
+   */
+  protected function setUpTerms() {
+    $parent_vid = 0;
+    foreach ($this->termTranslationMap as $name => $translation) {
+
+      $term = $this->createTerm([
+        'name' => $name,
+        'langcode' => $this->baseLangcode,
+        'parent' => $parent_vid,
+        'vid' => $this->vocabulary->id(),
+      ]);
+
+      $term->addTranslation($this->translateToLangcode, [
+        'name' => $translation,
+      ]);
+      $term->save();
+
+      // Each term is nested under the last.
+      $parent_vid = $term->id();
+
+      $this->terms[] = $term;
+    }
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/VocabularyLanguageTest.php

@@ -0,0 +1,137 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\language\Entity\ConfigurableLanguage;
+use Drupal\language\Entity\ContentLanguageSettings;
+
+/**
+ * Tests the language functionality for vocabularies.
+ *
+ * @group taxonomy
+ */
+class VocabularyLanguageTest extends TaxonomyTestBase {
+
+  protected static $modules = ['language'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    // Create an administrative user.
+    $this->drupalLogin($this->drupalCreateUser(['administer taxonomy']));
+
+    // Add some custom languages.
+    ConfigurableLanguage::create([
+      'id' => 'aa',
+      'label' => $this->randomMachineName(),
+    ])->save();
+
+    ConfigurableLanguage::create([
+      'id' => 'bb',
+      'label' => $this->randomMachineName(),
+    ])->save();
+  }
+
+  /**
+   * Tests language settings for vocabularies.
+   */
+  public function testVocabularyLanguage(): void {
+    $this->drupalGet('admin/structure/taxonomy/add');
+
+    // Check that we have the language selector available.
+    $this->assertSession()->fieldExists('edit-langcode');
+
+    // Create the vocabulary.
+    $vid = $this->randomMachineName();
+    $edit['name'] = $this->randomMachineName();
+    $edit['description'] = $this->randomMachineName();
+    $edit['langcode'] = 'aa';
+    $edit['vid'] = $vid;
+    $this->submitForm($edit, 'Save');
+
+    // Check the language on the edit page.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vid);
+    $this->assertTrue($this->assertSession()->optionExists('edit-langcode', $edit['langcode'])->isSelected());
+
+    // Change the language and save again.
+    $edit['langcode'] = 'bb';
+    unset($edit['vid']);
+    $this->submitForm($edit, 'Save');
+
+    // Check again the language on the edit page.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vid);
+    $this->assertTrue($this->assertSession()->optionExists('edit-langcode', $edit['langcode'])->isSelected());
+  }
+
+  /**
+   * Tests term language settings for vocabulary terms are saved and updated.
+   */
+  public function testVocabularyDefaultLanguageForTerms(): void {
+    // Add a new vocabulary and check that the default language settings are for
+    // the terms are saved.
+    $edit = [
+      'name' => $this->randomMachineName(),
+      'vid' => $this->randomMachineName(),
+      'default_language[langcode]' => 'bb',
+      'default_language[language_alterable]' => TRUE,
+    ];
+    $vid = $edit['vid'];
+    $this->drupalGet('admin/structure/taxonomy/add');
+    $this->submitForm($edit, 'Save');
+
+    // Check that the vocabulary was actually created.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $edit['vid']);
+    $this->assertSession()->statusCodeEquals(200);
+
+    // Check that the language settings were saved.
+    $language_settings = ContentLanguageSettings::loadByEntityTypeBundle('taxonomy_term', $edit['vid']);
+    $this->assertEquals('bb', $language_settings->getDefaultLangcode(), 'The langcode was saved.');
+    $this->assertTrue($language_settings->isLanguageAlterable(), 'The visibility setting was saved.');
+
+    // Check that the correct options are selected in the interface.
+    $this->assertTrue($this->assertSession()->optionExists('edit-default-language-langcode', 'bb')->isSelected());
+    $this->assertSession()->checkboxChecked('edit-default-language-language-alterable');
+
+    // Edit the vocabulary and check that the new settings are updated.
+    $edit = [
+      'default_language[langcode]' => 'aa',
+      'default_language[language_alterable]' => FALSE,
+    ];
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vid);
+    $this->submitForm($edit, 'Save');
+
+    // And check again the settings and also the interface.
+    $language_settings = ContentLanguageSettings::loadByEntityTypeBundle('taxonomy_term', $vid);
+    $this->assertEquals('aa', $language_settings->getDefaultLangcode(), 'The langcode was saved.');
+    $this->assertFalse($language_settings->isLanguageAlterable(), 'The visibility setting was saved.');
+
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vid);
+    $this->assertTrue($this->assertSession()->optionExists('edit-default-language-langcode', 'aa')->isSelected());
+    $this->assertSession()->checkboxNotChecked('edit-default-language-language-alterable');
+
+    // Check that language settings are changed after editing vocabulary.
+    $edit = [
+      'name' => $this->randomMachineName(),
+      'default_language[langcode]' => 'authors_default',
+      'default_language[language_alterable]' => FALSE,
+    ];
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vid);
+    $this->submitForm($edit, 'Save');
+
+    // Check that we have the new settings.
+    $new_settings = ContentLanguageSettings::loadByEntityTypeBundle('taxonomy_term', $vid);
+    $this->assertEquals('authors_default', $new_settings->getDefaultLangcode(), 'The langcode was saved.');
+    $this->assertFalse($new_settings->isLanguageAlterable(), 'The new visibility setting was saved.');
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/VocabularyPermissionsTest.php

@@ -0,0 +1,394 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Component\Utility\Unicode;
+
+/**
+ * Tests the taxonomy vocabulary permissions.
+ *
+ * @group taxonomy
+ */
+class VocabularyPermissionsTest extends TaxonomyTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['help'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->drupalPlaceBlock('page_title_block');
+    $this->drupalPlaceBlock('local_actions_block');
+    $this->drupalPlaceBlock('help_block');
+  }
+
+  /**
+   * Create, edit and delete a vocabulary via the user interface.
+   */
+  public function testVocabularyPermissionsVocabulary(): void {
+    // VocabularyTest.php already tests for user with "administer taxonomy"
+    // permission.
+
+    // Test as user without proper permissions.
+    $authenticated_user = $this->drupalCreateUser([]);
+    $this->drupalLogin($authenticated_user);
+
+    $assert_session = $this->assertSession();
+
+    // Visit the main taxonomy administration page.
+    $this->drupalGet('admin/structure/taxonomy');
+    $assert_session->statusCodeEquals(403);
+
+    // Test as user with "access taxonomy overview" permissions.
+    $proper_user = $this->drupalCreateUser(['access taxonomy overview']);
+    $this->drupalLogin($proper_user);
+
+    // Visit the main taxonomy administration page.
+    $this->drupalGet('admin/structure/taxonomy');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->pageTextContains('Vocabulary name');
+    $assert_session->linkNotExists('Add vocabulary');
+  }
+
+  /**
+   * Tests the vocabulary overview permission.
+   */
+  public function testTaxonomyVocabularyOverviewPermissions(): void {
+    // Create two vocabularies, one with two terms, the other without any term.
+    /** @var \Drupal\taxonomy\Entity\Vocabulary $vocabulary1 , $vocabulary2 */
+    $vocabulary1 = $this->createVocabulary();
+    $vocabulary2 = $this->createVocabulary();
+    $vocabulary1_id = $vocabulary1->id();
+    $vocabulary2_id = $vocabulary2->id();
+    $this->createTerm($vocabulary1);
+    $this->createTerm($vocabulary1);
+
+    // Assert expected help texts on first vocabulary.
+    $vocabulary1_label = Unicode::ucfirst($vocabulary1->label());
+    $edit_help_text = "You can reorganize the terms in $vocabulary1_label using their drag-and-drop handles, and group terms under a parent term by sliding them under and to the right of the parent.";
+    $no_edit_help_text = "$vocabulary1_label contains the following terms.";
+
+    $assert_session = $this->assertSession();
+
+    // Logged in as admin user with 'administer taxonomy' permission.
+    $admin_user = $this->drupalCreateUser(['administer taxonomy']);
+    $this->drupalLogin($admin_user);
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary1_id . '/overview');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->linkExists('Edit');
+    $assert_session->linkExists('Delete');
+    $assert_session->linkExists('Add term');
+    $assert_session->buttonExists('Save');
+    $assert_session->pageTextContains('Weight');
+    $assert_session->fieldExists('Weight');
+    $assert_session->pageTextContains($edit_help_text);
+
+    $this->submitForm([], 'Reset to alphabetical');
+    $assert_session->statusCodeEquals(200);
+
+    // Visit vocabulary overview without terms. 'Add term' should be shown.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary2_id . '/overview');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->pageTextContains('No terms available');
+    $assert_session->linkExists('Add term');
+
+    // Login as a user without any of the required permissions.
+    $no_permission_user = $this->drupalCreateUser();
+    $this->drupalLogin($no_permission_user);
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary1_id . '/overview');
+    $assert_session->statusCodeEquals(403);
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary2_id . '/overview');
+    $assert_session->statusCodeEquals(403);
+
+    // Log in as a user with only the overview permission, neither edit nor
+    // delete operations must be available and no Save button.
+    $overview_only_user = $this->drupalCreateUser(['access taxonomy overview']);
+    $this->drupalLogin($overview_only_user);
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary1_id . '/overview');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->linkNotExists('Edit');
+    $assert_session->linkNotExists('Delete');
+    $assert_session->buttonNotExists('Save');
+    $assert_session->buttonNotExists('Reset to alphabetical');
+    $assert_session->pageTextContains('Weight');
+    $assert_session->fieldNotExists('Weight');
+    $assert_session->linkNotExists('Add term');
+    $assert_session->pageTextContains($no_edit_help_text);
+
+    // Visit vocabulary overview without terms. 'Add term' should not be shown.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary2_id . '/overview');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->pageTextContains('No terms available');
+    $assert_session->linkNotExists('Add term');
+
+    // Login as a user with permission to edit terms, only edit link should be
+    // visible.
+    $edit_user = $this->createUser([
+      'access taxonomy overview',
+      'edit terms in ' . $vocabulary1_id,
+      'edit terms in ' . $vocabulary2_id,
+    ]);
+    $this->drupalLogin($edit_user);
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary1_id . '/overview');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->linkExists('Edit');
+    $assert_session->linkNotExists('Delete');
+    $assert_session->buttonExists('Save');
+    $assert_session->pageTextContains('Weight');
+    $assert_session->fieldExists('Weight');
+    $assert_session->linkNotExists('Add term');
+    $assert_session->pageTextContains($edit_help_text);
+
+    $this->submitForm([], 'Reset to alphabetical');
+    $assert_session->statusCodeEquals(200);
+
+    // Visit vocabulary overview without terms. 'Add term' should not be shown.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary2_id . '/overview');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->pageTextContains('No terms available');
+    $assert_session->linkNotExists('Add term');
+
+    // Login as a user with permission only to delete terms.
+    $edit_delete_user = $this->createUser([
+      'access taxonomy overview',
+      'delete terms in ' . $vocabulary1_id,
+      'delete terms in ' . $vocabulary2_id,
+    ]);
+    $this->drupalLogin($edit_delete_user);
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary1_id . '/overview');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->linkNotExists('Edit');
+    $assert_session->linkExists('Delete');
+    $assert_session->linkNotExists('Add term');
+    $assert_session->buttonNotExists('Save');
+    $assert_session->buttonNotExists('Reset to alphabetical');
+    $assert_session->pageTextContains('Weight');
+    $assert_session->fieldNotExists('Weight');
+    $assert_session->pageTextContains($no_edit_help_text);
+
+    // Visit vocabulary overview without terms. 'Add term' should not be shown.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary2_id . '/overview');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->pageTextContains('No terms available');
+    $assert_session->linkNotExists('Add term');
+
+    // Login as a user with permission to edit and delete terms.
+    $edit_delete_user = $this->createUser([
+      'access taxonomy overview',
+      'edit terms in ' . $vocabulary1_id,
+      'delete terms in ' . $vocabulary1_id,
+      'edit terms in ' . $vocabulary2_id,
+      'delete terms in ' . $vocabulary2_id,
+    ]);
+    $this->drupalLogin($edit_delete_user);
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary1_id . '/overview');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->linkExists('Edit');
+    $assert_session->linkExists('Delete');
+    $assert_session->linkNotExists('Add term');
+    $assert_session->buttonExists('Save');
+    $assert_session->pageTextContains('Weight');
+    $assert_session->fieldExists('Weight');
+    $assert_session->pageTextContains($edit_help_text);
+    $this->submitForm([], 'Reset to alphabetical');
+    $assert_session->statusCodeEquals(200);
+
+    // Visit vocabulary overview without terms. 'Add term' should not be shown.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary2_id . '/overview');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->pageTextContains('No terms available');
+    $assert_session->linkNotExists('Add term');
+
+    // Login as a user with permission to create new terms, only add new term
+    // link should be visible.
+    $edit_user = $this->createUser([
+      'access taxonomy overview',
+      'create terms in ' . $vocabulary1_id,
+      'create terms in ' . $vocabulary2_id,
+    ]);
+    $this->drupalLogin($edit_user);
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary1_id . '/overview');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->linkNotExists('Edit');
+    $assert_session->linkNotExists('Delete');
+    $assert_session->linkExists('Add term');
+    $assert_session->buttonNotExists('Save');
+    $assert_session->buttonNotExists('Reset to alphabetical');
+    $assert_session->pageTextContains('Weight');
+    $assert_session->fieldNotExists('Weight');
+    $assert_session->pageTextContains($no_edit_help_text);
+
+    // Visit vocabulary overview without terms. 'Add term' should not be shown.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary2_id . '/overview');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->pageTextContains('No terms available');
+    $assert_session->linkExists('Add term');
+
+    // Ensure the dynamic vocabulary permissions have the correct dependencies.
+    $permissions = \Drupal::service('user.permissions')->getPermissions();
+    $this->assertTrue(isset($permissions['create terms in ' . $vocabulary1_id]));
+    $this->assertEquals(['config' => [$vocabulary1->getConfigDependencyName()]], $permissions['create terms in ' . $vocabulary1_id]['dependencies']);
+  }
+
+  /**
+   * Create, edit and delete a taxonomy term via the user interface.
+   */
+  public function testVocabularyPermissionsTaxonomyTerm(): void {
+    // Vocabulary used for creating, removing and editing terms.
+    $vocabulary = $this->createVocabulary();
+
+    // Test as admin user.
+    $user = $this->drupalCreateUser(['administer taxonomy']);
+    $this->drupalLogin($user);
+
+    // Visit the main taxonomy administration page.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary->id() . '/add');
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSession()->fieldExists('edit-name-0-value');
+
+    // Submit the term.
+    $edit = [];
+    $edit['name[0][value]'] = $this->randomMachineName();
+
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextContains('Created new term ' . $edit['name[0][value]'] . '.');
+
+    // Verify that the creation message contains a link to a term.
+    $this->assertSession()->elementExists('xpath', '//div[@data-drupal-messages]//a[contains(@href, "term/")]');
+
+    $terms = \Drupal::entityTypeManager()
+      ->getStorage('taxonomy_term')
+      ->loadByProperties(['name' => $edit['name[0][value]']]);
+    $term = reset($terms);
+
+    // Edit the term.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSession()->pageTextContains($edit['name[0][value]']);
+
+    $edit['name[0][value]'] = $this->randomMachineName();
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextContains('Updated term ' . $edit['name[0][value]'] . '.');
+
+    // Delete the vocabulary.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/delete');
+    $this->assertSession()->pageTextContains("Are you sure you want to delete the taxonomy term {$edit['name[0][value]']}?");
+
+    // Confirm deletion.
+    $this->submitForm([], 'Delete');
+    $this->assertSession()->pageTextContains("Deleted term {$edit['name[0][value]']}.");
+
+    // Test as user with "create" permissions.
+    $user = $this->drupalCreateUser(["create terms in {$vocabulary->id()}"]);
+    $this->drupalLogin($user);
+
+    $assert_session = $this->assertSession();
+
+    // Create a new term.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary->id() . '/add');
+    $assert_session->statusCodeEquals(200);
+    $assert_session->fieldExists('name[0][value]');
+
+    // Submit the term.
+    $edit = [];
+    $edit['name[0][value]'] = $this->randomMachineName();
+
+    $this->submitForm($edit, 'Save');
+    $assert_session->pageTextContains("Created new term {$edit['name[0][value]']}.");
+
+    $terms = \Drupal::entityTypeManager()
+      ->getStorage('taxonomy_term')
+      ->loadByProperties(['name' => $edit['name[0][value]']]);
+    $term = reset($terms);
+
+    // Ensure that edit and delete access is denied.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $assert_session->statusCodeEquals(403);
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/delete');
+    $assert_session->statusCodeEquals(403);
+
+    // Test as user with "edit" permissions.
+    $user = $this->drupalCreateUser(["edit terms in {$vocabulary->id()}"]);
+    $this->drupalLogin($user);
+
+    // Ensure the taxonomy term add form is denied.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary->id() . '/add');
+    $this->assertSession()->statusCodeEquals(403);
+
+    // Create a test term.
+    $term = $this->createTerm($vocabulary);
+
+    // Edit the term.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSession()->pageTextContains($term->getName());
+
+    $edit['name[0][value]'] = $this->randomMachineName();
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextContains('Updated term ' . $edit['name[0][value]'] . '.');
+
+    // Verify that the update message contains a link to a term.
+    $this->assertSession()->elementExists('xpath', '//div[@data-drupal-messages]//a[contains(@href, "term/")]');
+
+    // Ensure the term cannot be deleted.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/delete');
+    $this->assertSession()->statusCodeEquals(403);
+
+    // Test as user with "delete" permissions.
+    $user = $this->drupalCreateUser(["delete terms in {$vocabulary->id()}"]);
+    $this->drupalLogin($user);
+
+    // Ensure the taxonomy term add form is denied.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary->id() . '/add');
+    $this->assertSession()->statusCodeEquals(403);
+
+    // Create a test term.
+    $term = $this->createTerm($vocabulary);
+
+    // Ensure that the term cannot be edited.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $this->assertSession()->statusCodeEquals(403);
+
+    // Delete the vocabulary.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/delete');
+    $this->assertSession()->pageTextContains("Are you sure you want to delete the taxonomy term {$term->getName()}?");
+
+    // Confirm deletion.
+    $this->submitForm([], 'Delete');
+    $this->assertSession()->pageTextContains("Deleted term {$term->getName()}.");
+
+    // Test as user without proper permissions.
+    $user = $this->drupalCreateUser();
+    $this->drupalLogin($user);
+
+    // Ensure the taxonomy term add form is denied.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary->id() . '/add');
+    $this->assertSession()->statusCodeEquals(403);
+
+    // Create a test term.
+    $term = $this->createTerm($vocabulary);
+
+    // Ensure that the term cannot be edited.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/edit');
+    $this->assertSession()->statusCodeEquals(403);
+
+    // Ensure the term cannot be deleted.
+    $this->drupalGet('taxonomy/term/' . $term->id() . '/delete');
+    $this->assertSession()->statusCodeEquals(403);
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/VocabularySerializationTest.php

@@ -0,0 +1,54 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\taxonomy\Entity\Vocabulary;
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Regression test for https://www.drupal.org/node/2807263.
+ *
+ * When a Vocabulary entity is unserialized before the modules have been loaded
+ * (which happens in the KernelPreHandle Stack middleware), then the constants
+ * that the Vocabulary entity uses are not yet available because they are set in
+ * taxonomy.module. This means that for example the PageCache middleware cannot
+ * load any cached Vocabulary entity, because unserialization will fail.
+ *
+ * @group taxonomy
+ */
+class VocabularySerializationTest extends BrowserTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['taxonomy', 'vocabulary_serialization_test'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    Vocabulary::create(['vid' => 'test', 'name' => 'Test'])->save();
+  }
+
+  public function testSerialization(): void {
+    $this->drupalGet('/vocabulary_serialization_test/test');
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSame('this is the output', $this->getSession()->getPage()->getContent());
+    $this->assertSession()->responseHeaderEquals('X-Drupal-Cache', 'MISS');
+
+    $this->drupalGet('/vocabulary_serialization_test/test');
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSame('this is the output', $this->getSession()->getPage()->getContent());
+    $this->assertSession()->responseHeaderEquals('X-Drupal-Cache', 'HIT');
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/VocabularyTranslationTest.php

@@ -0,0 +1,121 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\language\Entity\ConfigurableLanguage;
+
+/**
+ * Tests content translation for vocabularies.
+ *
+ * @group taxonomy
+ */
+class VocabularyTranslationTest extends TaxonomyTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'content_translation',
+    'language',
+    'config_translation',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Languages to enable.
+   *
+   * @var string[]
+   */
+  protected $additionalLangcodes = ['es'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    // Create an administrative user.
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer taxonomy',
+      'administer content translation',
+      'translate configuration',
+    ]));
+
+    // Add languages.
+    foreach ($this->additionalLangcodes as $langcode) {
+      ConfigurableLanguage::createFromLangcode($langcode)->save();
+    }
+  }
+
+  /**
+   * Tests language settings for vocabularies.
+   */
+  public function testVocabularyLanguage(): void {
+    $this->drupalGet('admin/structure/taxonomy/add');
+
+    // Check that the field to enable content translation is available.
+    $this->assertSession()->fieldExists('edit-default-language-content-translation');
+
+    // Create the vocabulary.
+    $vid = $this->randomMachineName();
+    $edit['name'] = $this->randomMachineName();
+    $edit['description'] = $this->randomMachineName();
+    $edit['langcode'] = 'en';
+    $edit['vid'] = $vid;
+    $edit['default_language[content_translation]'] = TRUE;
+    $this->submitForm($edit, 'Save');
+
+    // Check if content translation is enabled on the edit page.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vid);
+    $this->assertSession()->checkboxChecked('edit-default-language-content-translation');
+  }
+
+  /**
+   * Tests vocabulary name translation for the overview and reset pages.
+   */
+  public function testVocabularyTitleLabelTranslation(): void {
+    $this->drupalGet('admin/structure/taxonomy/add');
+
+    // Create the vocabulary.
+    $vid = $this->randomMachineName();
+    $edit['name'] = $this->randomMachineName();
+    $edit['description'] = $this->randomMachineName();
+    $edit['langcode'] = 'en';
+    $edit['vid'] = $vid;
+    $edit['default_language[content_translation]'] = TRUE;
+    $this->submitForm($edit, 'Save');
+
+    $langcode = $this->additionalLangcodes[0];
+    $vid_name = $edit['name'];
+    $translated_vid_name = "Translated $vid_name";
+
+    $this->assertSession()->pageTextContains($vid_name);
+
+    // Assert that the name label is displayed on the translation form with the
+    // right value.
+    $this->drupalGet("admin/structure/taxonomy/manage/$vid/translate/$langcode/add");
+
+    // Translate the name label.
+    $this->submitForm(["translation[config_names][taxonomy.vocabulary.$vid][name]" => $translated_vid_name], 'Save translation');
+
+    // Assert that the right name label is displayed on the taxonomy term
+    // overview page.
+    $this->drupalGet("admin/structure/taxonomy/manage/$vid/overview");
+    $this->assertSession()->pageTextContains($vid_name);
+    $this->drupalGet("$langcode/admin/structure/taxonomy/manage/$vid/overview");
+    $this->assertSession()->pageTextContains($translated_vid_name);
+
+    // Assert that the right name label is displayed on the taxonomy reset page.
+    $this->drupalGet("admin/structure/taxonomy/manage/$vid/reset");
+    $this->assertSession()->pageTextContains($vid_name);
+    $this->drupalGet("$langcode/admin/structure/taxonomy/manage/$vid/reset");
+    $this->assertSession()->pageTextContains($translated_vid_name);
+  }
+
+}

core/modules/taxonomy/tests/src/Functional/VocabularyUiTest.php

@@ -0,0 +1,189 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Functional;
+
+use Drupal\Component\Render\FormattableMarkup;
+use Drupal\Core\Url;
+use Drupal\taxonomy\Entity\Vocabulary;
+
+/**
+ * Tests the taxonomy vocabulary interface.
+ *
+ * @group taxonomy
+ */
+class VocabularyUiTest extends TaxonomyTestBase {
+
+  /**
+   * The vocabulary used for creating terms.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->drupalLogin($this->drupalCreateUser(['administer taxonomy']));
+    $this->vocabulary = $this->createVocabulary();
+    $this->drupalPlaceBlock('local_actions_block');
+    $this->drupalPlaceBlock('page_title_block');
+  }
+
+  /**
+   * Create, edit and delete a vocabulary via the user interface.
+   */
+  public function testVocabularyInterface(): void {
+    // Visit the main taxonomy administration page.
+    $this->drupalGet('admin/structure/taxonomy');
+
+    // Create a new vocabulary.
+    $this->clickLink('Add vocabulary');
+    $edit = [];
+    $vid = $this->randomMachineName();
+    $edit['name'] = $this->randomMachineName();
+    $edit['description'] = $this->randomMachineName();
+    $edit['vid'] = $vid;
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextContains("Created new vocabulary {$edit['name']}.");
+
+    // Edit the vocabulary.
+    $this->drupalGet('admin/structure/taxonomy');
+    $this->assertSession()->pageTextContains($edit['name']);
+    $this->assertSession()->pageTextContains($edit['description']);
+    $this->assertSession()->linkByHrefExists(Url::fromRoute('entity.taxonomy_term.add_form', ['taxonomy_vocabulary' => $edit['vid']])->toString());
+    $this->clickLink('Edit vocabulary');
+    $edit = [];
+    $edit['name'] = $this->randomMachineName();
+    $edit['description'] = $this->randomMachineName();
+    $this->submitForm($edit, 'Save');
+    $this->drupalGet('admin/structure/taxonomy');
+    $this->assertSession()->pageTextContains($edit['name']);
+    $this->assertSession()->pageTextContains($edit['description']);
+
+    // Try to submit a vocabulary with a duplicate machine name.
+    $edit['vid'] = $vid;
+    $this->drupalGet('admin/structure/taxonomy/add');
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextContains('The machine-readable name is already in use. It must be unique.');
+
+    // Try to submit an invalid machine name.
+    $edit['vid'] = '!&^%';
+    $this->drupalGet('admin/structure/taxonomy/add');
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextContains('The machine-readable name must contain only lowercase letters, numbers, and underscores.');
+
+    // Ensure that vocabulary titles are escaped properly.
+    $edit = [];
+    $edit['name'] = 'Don\'t Panic';
+    $edit['description'] = $this->randomMachineName();
+    $edit['vid'] = 'don_t_panic';
+    $this->drupalGet('admin/structure/taxonomy/add');
+    $this->submitForm($edit, 'Save');
+
+    $site_name = $this->config('system.site')->get('name');
+    $this->assertSession()->titleEquals("Don't Panic | $site_name");
+
+    // Delete the vocabulary.
+    $this->drupalGet('admin/structure/taxonomy');
+    $href = Url::fromRoute('entity.taxonomy_vocabulary.delete_form', ['taxonomy_vocabulary' => $edit['vid']])->toString();
+    $xpath = $this->assertSession()->buildXPathQuery('//a[contains(@href, :href)]', [':href' => $href]);
+    $link = $this->assertSession()->elementExists('xpath', $xpath);
+    $this->assertEquals('Delete vocabulary', $link->getText());
+    $link->click();
+
+    // Confirm deletion.
+    $this->assertSession()->responseContains(new FormattableMarkup('Are you sure you want to delete the vocabulary %name?', ['%name' => $edit['name']]));
+    $this->submitForm([], 'Delete');
+    $this->assertSession()->responseContains(new FormattableMarkup('Deleted vocabulary %name.', ['%name' => $edit['name']]));
+    $this->container->get('entity_type.manager')->getStorage('taxonomy_vocabulary')->resetCache();
+    $this->assertNull(Vocabulary::load($edit['vid']), 'Vocabulary not found.');
+  }
+
+  /**
+   * Changing weights on the vocabulary overview with two or more vocabularies.
+   */
+  public function testTaxonomyAdminChangingWeights(): void {
+    // Create some vocabularies.
+    for ($i = 0; $i < 10; $i++) {
+      $this->createVocabulary();
+    }
+    // Get all vocabularies and change their weights.
+    $vocabularies = Vocabulary::loadMultiple();
+    $edit = [];
+    foreach ($vocabularies as $key => $vocabulary) {
+      $weight = -$vocabulary->get('weight');
+      $vocabularies[$key]->set('weight', $weight);
+      $edit['vocabularies[' . $key . '][weight]'] = $weight;
+    }
+    // Saving the new weights via the interface.
+    $this->drupalGet('admin/structure/taxonomy');
+    $this->submitForm($edit, 'Save');
+
+    // Load the vocabularies from the database.
+    $this->container->get('entity_type.manager')->getStorage('taxonomy_vocabulary')->resetCache();
+    $new_vocabularies = Vocabulary::loadMultiple();
+
+    // Check that the weights are saved in the database correctly.
+    foreach ($vocabularies as $key => $vocabulary) {
+      $this->assertEquals($new_vocabularies[$key]->get('weight'), $vocabularies[$key]->get('weight'), 'The vocabulary weight was changed.');
+    }
+  }
+
+  /**
+   * Tests the vocabulary overview with no vocabularies.
+   */
+  public function testTaxonomyAdminNoVocabularies(): void {
+    // Delete all vocabularies.
+    $vocabularies = Vocabulary::loadMultiple();
+    foreach ($vocabularies as $key => $vocabulary) {
+      $vocabulary->delete();
+    }
+    // Confirm that no vocabularies are found in the database.
+    $this->assertEmpty(Vocabulary::loadMultiple(), 'No vocabularies found.');
+    $this->drupalGet('admin/structure/taxonomy');
+    // Check the default message for no vocabularies.
+    $this->assertSession()->pageTextContains('No vocabularies available.');
+  }
+
+  /**
+   * Deleting a vocabulary.
+   */
+  public function testTaxonomyAdminDeletingVocabulary(): void {
+    // Create a vocabulary.
+    $vid = $this->randomMachineName();
+    $edit = [
+      'name' => $this->randomMachineName(),
+      'vid' => $vid,
+    ];
+    $this->drupalGet('admin/structure/taxonomy/add');
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextContains('Created new vocabulary');
+
+    // Check the created vocabulary.
+    $this->container->get('entity_type.manager')->getStorage('taxonomy_vocabulary')->resetCache();
+    $vocabulary = Vocabulary::load($vid);
+    $this->assertNotEmpty($vocabulary, 'Vocabulary found.');
+
+    // Delete the vocabulary.
+    $this->drupalGet('admin/structure/taxonomy/manage/' . $vocabulary->id());
+    $this->clickLink('Delete');
+    $this->assertSession()->pageTextContains("Are you sure you want to delete the vocabulary {$vocabulary->label()}?");
+    $this->assertSession()->pageTextContains('Deleting a vocabulary will delete all the terms in it. This action cannot be undone.');
+
+    // Confirm deletion.
+    $this->submitForm([], 'Delete');
+    $this->assertSession()->pageTextContains("Deleted vocabulary {$vocabulary->label()}.");
+    $this->container->get('entity_type.manager')->getStorage('taxonomy_vocabulary')->resetCache();
+    $this->assertNull(Vocabulary::load($vid), 'Vocabulary not found.');
+  }
+
+}

core/modules/taxonomy/tests/src/Kernel/ContextProvider/TermContextTest.php

@@ -0,0 +1,73 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Kernel\ContextProvider;
+
+use Drupal\Core\Routing\RouteMatch;
+use Drupal\KernelTests\KernelTestBase;
+use Drupal\taxonomy\ContextProvider\TermRouteContext;
+use Drupal\Tests\taxonomy\Traits\TaxonomyTestTrait;
+
+/**
+ * @coversDefaultClass \Drupal\taxonomy\ContextProvider\TermRouteContext
+ *
+ * @group taxonomy
+ */
+class TermContextTest extends KernelTestBase {
+
+  use TaxonomyTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['filter', 'taxonomy', 'text', 'user'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->installConfig(['filter']);
+    $this->installEntitySchema('user');
+    $this->installEntitySchema('taxonomy_term');
+  }
+
+  /**
+   * @covers ::getAvailableContexts
+   */
+  public function testGetAvailableContexts(): void {
+    $context_repository = $this->container->get('context.repository');
+
+    // Test taxonomy_term.taxonomy_term_route_context:taxonomy_term exists.
+    $contexts = $context_repository->getAvailableContexts();
+    $this->assertArrayHasKey('@taxonomy_term.taxonomy_term_route_context:taxonomy_term', $contexts);
+    $this->assertSame('entity:taxonomy_term', $contexts['@taxonomy_term.taxonomy_term_route_context:taxonomy_term']->getContextDefinition()
+      ->getDataType());
+  }
+
+  /**
+   * @covers ::getRuntimeContexts
+   */
+  public function testGetRuntimeContexts(): void {
+    // Create term.
+    $vocabulary = $this->createVocabulary();
+    $term = $this->createTerm($vocabulary);
+
+    // Create RouteMatch from term entity.
+    $url = $term->toUrl();
+    $route_provider = \Drupal::service('router.route_provider');
+    $route = $route_provider->getRouteByName($url->getRouteName());
+    $route_match = new RouteMatch($url->getRouteName(), $route, [
+      'taxonomy_term' => $term,
+    ]);
+
+    // Initiate TermRouteContext with RouteMatch.
+    $provider = new TermRouteContext($route_match);
+
+    $runtime_contexts = $provider->getRuntimeContexts([]);
+    $this->assertArrayHasKey('taxonomy_term', $runtime_contexts);
+    $this->assertTrue($runtime_contexts['taxonomy_term']->hasContextValue());
+  }
+
+}

core/modules/taxonomy/tests/src/Kernel/LoadMultipleTest.php

@@ -0,0 +1,82 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Kernel;
+
+use Drupal\KernelTests\KernelTestBase;
+use Drupal\taxonomy\Entity\Term;
+use Drupal\Tests\taxonomy\Traits\TaxonomyTestTrait;
+
+/**
+ * Tests the loading of multiple taxonomy terms at once.
+ *
+ * @group taxonomy
+ */
+class LoadMultipleTest extends KernelTestBase {
+
+  use TaxonomyTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'system',
+    'taxonomy',
+    'user',
+    'text',
+    'filter',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->installEntitySchema('taxonomy_term');
+  }
+
+  /**
+   * Tests loading multiple taxonomy terms by term ID and vocabulary.
+   */
+  public function testTaxonomyTermMultipleLoad(): void {
+    // Create a vocabulary.
+    $vocabulary = $this->createVocabulary();
+
+    // Create five terms in the vocabulary.
+    $i = 0;
+    while ($i < 5) {
+      $i++;
+      $this->createTerm($vocabulary);
+    }
+    // Load the terms from the vocabulary.
+    $term_storage = \Drupal::entityTypeManager()->getStorage('taxonomy_term');
+    $terms = $term_storage->loadByProperties(['vid' => $vocabulary->id()]);
+    $count = count($terms);
+    $this->assertEquals(5, $count, "Correct number of terms were loaded. $count terms.");
+
+    // Load the same terms again by tid.
+    $terms2 = Term::loadMultiple(array_keys($terms));
+    $this->assertEquals($terms, $terms2, 'Both arrays contain the same terms.');
+
+    // Remove one term from the array, then delete it.
+    $deleted = array_shift($terms2);
+    $deleted->delete();
+    $deleted_term = Term::load($deleted->id());
+    $this->assertNull($deleted_term);
+
+    // Load terms from the vocabulary by vid.
+    $terms3 = $term_storage->loadByProperties(['vid' => $vocabulary->id()]);
+    $this->assertCount(4, $terms3, 'Correct number of terms were loaded.');
+    $this->assertFalse(isset($terms3[$deleted->id()]));
+
+    // Create a single term and load it by name.
+    $term = $this->createTerm($vocabulary);
+    $loaded_terms = $term_storage->loadByProperties(['name' => $term->getName()]);
+    $this->assertCount(1, $loaded_terms, 'One term was loaded.');
+    $loaded_term = reset($loaded_terms);
+    $this->assertEquals($term->id(), $loaded_term->id(), 'Term loaded by name successfully.');
+  }
+
+}

core/modules/taxonomy/tests/src/Kernel/Migrate/MigrateTaxonomyConfigsTest.php

@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Kernel\Migrate;
+
+use Drupal\Tests\SchemaCheckTestTrait;
+use Drupal\Tests\migrate_drupal\Kernel\d6\MigrateDrupal6TestBase;
+
+/**
+ * Upgrade variables to taxonomy.settings.yml.
+ *
+ * @group migrate_drupal_6
+ */
+class MigrateTaxonomyConfigsTest extends MigrateDrupal6TestBase {
+
+  use SchemaCheckTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['taxonomy'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->executeMigration('taxonomy_settings');
+  }
+
+  /**
+   * Tests migration of taxonomy variables to taxonomy.settings.yml.
+   */
+  public function testTaxonomySettings(): void {
+    $config = $this->config('taxonomy.settings');
+    $this->assertSame(100, $config->get('terms_per_page_admin'));
+    $this->assertFalse($config->get('override_selector'));
+    $this->assertTrue($config->get('maintain_index_table'));
+    $this->assertConfigSchema(\Drupal::service('config.typed'), 'taxonomy.settings', $config->get());
+  }
+
+}

core/modules/taxonomy/tests/src/Kernel/Migrate/MigrateTaxonomyTermStubTest.php

@@ -0,0 +1,88 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Kernel\Migrate;
+
+use Drupal\migrate\MigrateExecutable;
+use Drupal\Tests\migrate_drupal\Kernel\MigrateDrupalTestBase;
+use Drupal\migrate_drupal\Tests\StubTestTrait;
+use Drupal\taxonomy\Entity\Term;
+use Drupal\taxonomy\Entity\Vocabulary;
+
+/**
+ * Test stub creation for taxonomy terms.
+ *
+ * @group taxonomy
+ */
+class MigrateTaxonomyTermStubTest extends MigrateDrupalTestBase {
+
+  use StubTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['taxonomy', 'text', 'taxonomy_term_stub_test'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->installEntitySchema('taxonomy_term');
+  }
+
+  /**
+   * Tests creation of taxonomy term stubs.
+   */
+  public function testStub(): void {
+    Vocabulary::create([
+      'vid' => 'test_vocabulary',
+      'name' => 'Test vocabulary',
+    ])->save();
+    $this->performStubTest('taxonomy_term');
+  }
+
+  /**
+   * Tests creation of stubs when weight is mapped.
+   */
+  public function testStubWithWeightMapping(): void {
+    // Create a vocabulary via migration for the terms to reference.
+    $vocabulary_data_rows = [
+      ['id' => '1', 'name' => 'tags'],
+    ];
+    $ids = ['id' => ['type' => 'integer']];
+    $definition = [
+      'migration_tags' => ['Stub test'],
+      'source' => [
+        'plugin' => 'embedded_data',
+        'data_rows' => $vocabulary_data_rows,
+        'ids' => $ids,
+      ],
+      'process' => [
+        'vid' => 'id',
+        'name' => 'name',
+      ],
+      'destination' => ['plugin' => 'entity:taxonomy_vocabulary'],
+    ];
+    $vocabulary_migration = \Drupal::service('plugin.manager.migration')->createStubMigration($definition);
+    $vocabulary_executable = new MigrateExecutable($vocabulary_migration, $this);
+    $vocabulary_executable->import();
+
+    // We have a term referencing an unmigrated parent, forcing a stub to be
+    // created.
+    $migration = $this->getMigration('taxonomy_term_stub_test');
+    $term_executable = new MigrateExecutable($migration, $this);
+    $term_executable->import();
+    $this->assertNotEmpty($migration->getIdMap()->getRowBySource(['2']), 'Stub row exists in the ID map table');
+
+    // Load the referenced term, which should exist as a stub.
+    /** @var \Drupal\Core\Entity\ContentEntityBase $stub_entity */
+    $stub_entity = Term::load(2);
+    $this->assertNotEmpty($stub_entity, 'Stub successfully created');
+    if ($stub_entity) {
+      $this->assertCount(0, $stub_entity->validate(), 'Stub is a valid entity');
+    }
+  }
+
+}

core/modules/taxonomy/tests/src/Kernel/Migrate/TaxonomyTermDeriverTest.php

@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Kernel\Migrate;
+
+use Drupal\Tests\migrate_drupal\Kernel\d7\MigrateDrupal7TestBase;
+
+// cspell:ignore vocabfixed vocablocalized vocabtranslate
+
+/**
+ * Tests d7 taxonomy term deriver.
+ *
+ * @group migrate_drupal_7
+ */
+class TaxonomyTermDeriverTest extends MigrateDrupal7TestBase {
+
+  protected static $modules = ['taxonomy', 'text'];
+
+  /**
+   * Tests fields exist in  process pipeline for term migrations.
+   */
+  public function testBuilder(): void {
+    // Test a field on the vocabfixed term.
+    $process = $this->getMigration('d7_taxonomy_term:vocabfixed')->getProcess();
+    $this->assertSame('field_training', $process['field_training'][0]['source']);
+
+    // Test a field on the vocablocalized term.
+    $process = $this->getMigration('d7_taxonomy_term:vocablocalized')->getProcess();
+    $this->assertSame('field_sector', $process['field_sector'][0]['source']);
+
+    // Test a field on the vocabtranslate term.
+    $process = $this->getMigration('d7_taxonomy_term:vocabtranslate')->getProcess();
+    $this->assertSame('field_chancellor', $process['field_chancellor'][0]['source']);
+
+    // Test a field on the test_vocabulary term.
+    $process = $this->getMigration('d7_taxonomy_term:test_vocabulary')->getProcess();
+    $this->assertSame('field_integer', $process['field_integer'][0]['source']);
+    $this->assertSame('field_term_reference', $process['field_term_reference'][0]['source']);
+  }
+
+}

core/modules/taxonomy/tests/src/Kernel/Migrate/d6/MigrateTaxonomyTermTest.php

@@ -0,0 +1,120 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Kernel\Migrate\d6;
+
+use Drupal\taxonomy\Entity\Term;
+use Drupal\Tests\migrate_drupal\Kernel\d6\MigrateDrupal6TestBase;
+
+/**
+ * Upgrade taxonomy terms.
+ *
+ * @group migrate_drupal_6
+ */
+class MigrateTaxonomyTermTest extends MigrateDrupal6TestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['comment', 'taxonomy'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->installEntitySchema('taxonomy_term');
+    $this->executeMigrations(['d6_taxonomy_vocabulary', 'd6_taxonomy_term']);
+  }
+
+  /**
+   * Tests the Drupal 6 taxonomy term to Drupal 8 migration.
+   */
+  public function testTaxonomyTerms(): void {
+    $expected_results = [
+      '1' => [
+        'source_vid' => 1,
+        'vid' => 'vocabulary_1_i_0_',
+        'weight' => 0,
+        'parent' => [0],
+        'language' => 'zu',
+      ],
+      '2' => [
+        'source_vid' => 2,
+        'vid' => 'vocabulary_2_i_1_',
+        'weight' => 3,
+        'parent' => [0],
+        'language' => 'fr',
+      ],
+      '3' => [
+        'source_vid' => 2,
+        'vid' => 'vocabulary_2_i_1_',
+        'weight' => 4,
+        'parent' => [2],
+        'language' => 'fr',
+      ],
+      '4' => [
+        'source_vid' => 3,
+        'vid' => 'vocabulary_3_i_2_',
+        'weight' => 6,
+        'parent' => [0],
+      ],
+      '5' => [
+        'source_vid' => 3,
+        'vid' => 'vocabulary_3_i_2_',
+        'weight' => 7,
+        'parent' => [4],
+      ],
+      '6' => [
+        'source_vid' => 3,
+        'vid' => 'vocabulary_3_i_2_',
+        'weight' => 8,
+        'parent' => [4, 5],
+      ],
+    ];
+    $terms = Term::loadMultiple(array_keys($expected_results));
+
+    // Find each term in the tree.
+    $storage = \Drupal::entityTypeManager()->getStorage('taxonomy_term');
+    $vids = array_unique(array_column($expected_results, 'vid'));
+    $tree_terms = [];
+    foreach ($vids as $vid) {
+      foreach ($storage->loadTree($vid) as $term) {
+        $tree_terms[$term->tid] = $term;
+      }
+    }
+
+    foreach ($expected_results as $tid => $values) {
+      /** @var \Drupal\taxonomy\Entity\Term $term */
+      $term = $terms[$tid];
+      $language = isset($values['language']) ? $values['language'] . ' - ' : '';
+      $this->assertSame("{$language}term {$tid} of vocabulary {$values['source_vid']}", $term->name->value);
+      $this->assertSame("{$language}description of term {$tid} of vocabulary {$values['source_vid']}", $term->description->value);
+      $this->assertSame($values['vid'], $term->vid->target_id);
+      $this->assertSame((string) $values['weight'], $term->weight->value);
+      if ($values['parent'] === [0]) {
+        $this->assertSame(0, (int) $term->parent->target_id);
+      }
+      else {
+        $parents = [];
+        foreach (\Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadParents($tid) as $parent) {
+          $parents[] = (int) $parent->id();
+        }
+        $this->assertSame($parents, $values['parent']);
+      }
+
+      $this->assertArrayHasKey($tid, $tree_terms, "Term $tid exists in vocabulary tree");
+      $tree_term = $tree_terms[$tid];
+
+      // PostgreSQL, MySQL and SQLite may not return the parent terms in the
+      // same order so sort before testing.
+      $expected_parents = $values['parent'];
+      sort($expected_parents);
+      $actual_parents = $tree_term->parents;
+      sort($actual_parents);
+      $this->assertEquals($expected_parents, $actual_parents, "Term $tid has correct parents in vocabulary tree");
+    }
+  }
+
+}

core/modules/taxonomy/tests/src/Kernel/Migrate/d6/MigrateTaxonomyVocabularyTest.php

@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Kernel\Migrate\d6;
+
+use Drupal\taxonomy\Entity\Vocabulary;
+use Drupal\Tests\migrate_drupal\Kernel\d6\MigrateDrupal6TestBase;
+
+/**
+ * Migrate taxonomy vocabularies to taxonomy.vocabulary.*.yml.
+ *
+ * @group migrate_drupal_6
+ */
+class MigrateTaxonomyVocabularyTest extends MigrateDrupal6TestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['taxonomy'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->executeMigration('d6_taxonomy_vocabulary');
+  }
+
+  /**
+   * Tests the Drupal 6 taxonomy vocabularies to Drupal 8 migration.
+   */
+  public function testTaxonomyVocabulary(): void {
+    for ($i = 0; $i < 3; $i++) {
+      $j = $i + 1;
+      $vocabulary = Vocabulary::load("vocabulary_{$j}_i_{$i}_");
+      $this->assertSame($this->getMigration('d6_taxonomy_vocabulary')->getIdMap()->lookupDestinationIds([$j]), [[$vocabulary->id()]]);
+      $this->assertSame("vocabulary $j (i=$i)", $vocabulary->label());
+      $this->assertSame("description of vocabulary $j (i=$i)", $vocabulary->getDescription());
+      $this->assertSame(4 + $i, $vocabulary->get('weight'));
+    }
+    $vocabulary = Vocabulary::load('vocabulary_name_much_longer_th');
+    $this->assertSame('vocabulary name much longer than thirty two characters', $vocabulary->label());
+    $this->assertSame('description of vocabulary name much longer than thirty two characters', $vocabulary->getDescription());
+    $this->assertSame(7, $vocabulary->get('weight'));
+  }
+
+}

core/modules/taxonomy/tests/src/Kernel/Migrate/d6/MigrateTaxonomyVocabularyTranslationTest.php

@@ -0,0 +1,56 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\taxonomy\Kernel\Migrate\d6;
+
+use Drupal\Tests\migrate_drupal\Kernel\d6\MigrateDrupal6TestBase;
+
+/**
+ * Migrate taxonomy vocabularies to taxonomy.vocabulary.*.yml.
+ *
+ * @group migrate_drupal_6
+ */
+class MigrateTaxonomyVocabularyTranslationTest extends MigrateDrupal6TestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'config_translation',
+    'language',
+    'taxonomy',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->executeMigrations([
+      'language',
+      'd6_taxonomy_vocabulary',
+      'd6_taxonomy_vocabulary_translation',
+    ]);
+  }
+
+  /**
+   * Tests the Drupal 6 i18n taxonomy vocabularies to Drupal 8 migration.
+   */
+  public function testTaxonomyVocabularyTranslation(): void {
+    $language_manager = \Drupal::service('language_manager');
+    $config = $language_manager->getLanguageConfigOverride('zu', 'taxonomy.vocabulary.vocabulary_1_i_0_');
+    $this->assertSame('zu - vocabulary 1 (i=0)', $config->get('name'));
+    $config = $language_manager->getLanguageConfigOverride('fr', 'taxonomy.vocabulary.vocabulary_1_i_0_');
+    $this->assertSame('fr - vocabulary 1 (i=0)', $config->get('name'));
+    $config = $language_manager->getLanguageConfigOverride('fr', 'taxonomy.vocabulary.vocabulary_2_i_1_');
+    $this->assertSame('fr - vocabulary 2 (i=1)', $config->get('name'));
+    $config = $language_manager->getLanguageConfigOverride('fr', 'taxonomy.vocabulary.vocabulary_3_i_2_');
+    $this->assertSame('fr - vocabulary 3 (i=2)', $config->get('name'));
+    $config = $language_manager->getLanguageConfigOverride('fr', 'taxonomy.vocabulary.vocabulary_name_much_longer_th');
+    $this->assertSame('Nom de vocabulaire beaucoup plus long que trente-deux caractères', $config->get('name'));
+    $config = $language_manager->getLanguageConfigOverride('fr', 'taxonomy.vocabulary.tags');
+    $this->assertSame('fr - Tags', $config->get('name'));
+  }
+
+}