first commit

core/modules/book/tests/modules/book_breadcrumb_test/book_breadcrumb_test.info.yml

@@ -0,0 +1,10 @@
+name: 'Book module breadcrumb tests'
+type: module
+description: 'Support module for book module breadcrumb 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/book/tests/modules/book_breadcrumb_test/book_breadcrumb_test.module

@@ -0,0 +1,27 @@
+<?php
+
+/**
+ * @file
+ * Test module for testing the book module breadcrumb.
+ */
+
+use Drupal\Core\Access\AccessResultForbidden;
+use Drupal\Core\Access\AccessResultNeutral;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\node\NodeInterface;
+
+/**
+ * Implements hook_ENTITY_TYPE_access().
+ */
+function book_breadcrumb_test_node_access(NodeInterface $node, $operation, AccountInterface $account) {
+  $config = \Drupal::config('book_breadcrumb_test.settings');
+  if ($config->get('hide') && $node->getTitle() == "you can't see me" && $operation == 'view') {
+    $access = new AccessResultForbidden();
+  }
+  else {
+    $access = new AccessResultNeutral();
+  }
+  $access->addCacheableDependency($config);
+  $access->addCacheableDependency($node);
+  return $access;
+}

core/modules/book/tests/modules/book_test/book_test.info.yml

@@ -0,0 +1,10 @@
+name: 'Book module tests'
+type: module
+description: 'Support module for book module 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/book/tests/modules/book_test/book_test.module

@@ -0,0 +1,22 @@
+<?php
+
+/**
+ * @file
+ * Test module for testing the book module.
+ *
+ * This module's functionality depends on the following state variables:
+ * - book_test.debug_book_navigation_cache_context: Used in NodeQueryAlterTest to enable the
+ *   node_access_all grant realm.
+ *
+ * @see \Drupal\book\Tests\BookTest::testBookNavigationCacheContext()
+ */
+
+/**
+ * Implements hook_page_attachments().
+ */
+function book_test_page_attachments(array &$page) {
+  $page['#cache']['tags'][] = 'book_test.debug_book_navigation_cache_context';
+  if (\Drupal::state()->get('book_test.debug_book_navigation_cache_context', FALSE)) {
+    \Drupal::messenger()->addStatus(\Drupal::service('cache_contexts_manager')->convertTokensToKeys(['route.book_navigation'])->getKeys()[0]);
+  }
+}

core/modules/book/tests/modules/book_test_views/book_test_views.info.yml

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

core/modules/book/tests/src/Functional/BookBreadcrumbTest.php

@@ -0,0 +1,220 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Create a book, add pages, and test book interface.
+ *
+ * @group book
+ * @group legacy
+ */
+class BookBreadcrumbTest extends BrowserTestBase {
+
+  /**
+   * Modules to install.
+   *
+   * @var array
+   */
+  protected static $modules = ['book', 'block', 'book_breadcrumb_test'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * A book node.
+   *
+   * @var \Drupal\node\NodeInterface
+   */
+  protected $book;
+
+  /**
+   * A user with permission to create and edit books.
+   *
+   * @var \Drupal\user\Entity\User
+   */
+  protected $bookAuthor;
+
+  /**
+   * A user without the 'node test view' permission.
+   *
+   * @var \Drupal\user\UserInterface
+   */
+  protected $webUserWithoutNodeAccess;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->drupalPlaceBlock('system_breadcrumb_block');
+    $this->drupalPlaceBlock('page_title_block');
+
+    // Create users.
+    $this->bookAuthor = $this->drupalCreateUser([
+      'create new books',
+      'create book content',
+      'edit own book content',
+      'add content to books',
+    ]);
+  }
+
+  /**
+   * Creates a new book with a page hierarchy.
+   *
+   * @return \Drupal\node\NodeInterface[]
+   *   The created book nodes.
+   */
+  protected function createBreadcrumbBook() {
+    // Create new book.
+    $this->drupalLogin($this->bookAuthor);
+
+    $this->book = $this->createBookNode('new');
+    $book = $this->book;
+
+    /*
+     * Add page hierarchy to book.
+     * Book
+     *  |- Node 0
+     *   |- Node 1
+     *   |- Node 2
+     *    |- Node 3
+     *     |- Node 4
+     *      |- Node 5
+     *  |- Node 6
+     */
+    $nodes = [];
+    $nodes[0] = $this->createBookNode($book->id());
+    $nodes[1] = $this->createBookNode($book->id(), $nodes[0]->id());
+    $nodes[2] = $this->createBookNode($book->id(), $nodes[0]->id());
+    $nodes[3] = $this->createBookNode($book->id(), $nodes[2]->id());
+    $nodes[4] = $this->createBookNode($book->id(), $nodes[3]->id());
+    $nodes[5] = $this->createBookNode($book->id(), $nodes[4]->id());
+    $nodes[6] = $this->createBookNode($book->id());
+
+    $this->drupalLogout();
+
+    return $nodes;
+  }
+
+  /**
+   * Creates a book node.
+   *
+   * @param int|string $book_nid
+   *   A book node ID or set to 'new' to create a new book.
+   * @param int|null $parent
+   *   (optional) Parent book reference ID. Defaults to NULL.
+   *
+   * @return \Drupal\node\NodeInterface
+   *   The created node.
+   */
+  protected function createBookNode($book_nid, $parent = NULL) {
+    // $number does not use drupal_static as it should not be reset since it
+    // uniquely identifies each call to createBookNode(). It is used to ensure
+    // that when sorted nodes stay in same order.
+    static $number = 0;
+
+    $edit = [];
+    $edit['title[0][value]'] = str_pad((string) $number, 2, '0', STR_PAD_LEFT) . ' - test node ' . $this->randomMachineName(10);
+    $edit['body[0][value]'] = 'test body ' . $this->randomMachineName(32) . ' ' . $this->randomMachineName(32);
+    $edit['book[bid]'] = $book_nid;
+
+    if ($parent !== NULL) {
+      $this->drupalGet('node/add/book');
+      $this->submitForm($edit, 'Change book (update list of parents)');
+
+      $edit['book[pid]'] = $parent;
+      $this->submitForm($edit, 'Save');
+      // Make sure the parent was flagged as having children.
+      $parent_node = \Drupal::entityTypeManager()->getStorage('node')->loadUnchanged($parent);
+      $this->assertNotEmpty($parent_node->book['has_children'], 'Parent node is marked as having children');
+    }
+    else {
+      $this->drupalGet('node/add/book');
+      $this->submitForm($edit, 'Save');
+    }
+
+    // Check to make sure the book node was created.
+    $node = $this->drupalGetNodeByTitle($edit['title[0][value]']);
+    $this->assertNotNull(($node === FALSE ? NULL : $node), 'Book node found in database.');
+    $number++;
+
+    return $node;
+  }
+
+  /**
+   * Tests that the breadcrumb is updated when book content changes.
+   */
+  public function testBreadcrumbTitleUpdates(): void {
+    // Create a new book.
+    $nodes = $this->createBreadcrumbBook();
+    $book = $this->book;
+
+    $this->drupalLogin($this->bookAuthor);
+
+    $this->drupalGet($nodes[4]->toUrl());
+    // Fetch each node title in the current breadcrumb.
+    $links = $this->xpath('//nav[@aria-labelledby="system-breadcrumb"]/ol/li/a');
+    $got_breadcrumb = [];
+    foreach ($links as $link) {
+      $got_breadcrumb[] = $link->getText();
+    }
+    // Home link and four parent book nodes should be in the breadcrumb.
+    $this->assertCount(5, $got_breadcrumb);
+    $this->assertEquals($nodes[3]->getTitle(), end($got_breadcrumb));
+    $edit = [
+      'title[0][value]' => 'Updated node5 title',
+    ];
+    $this->drupalGet($nodes[3]->toUrl('edit-form'));
+    $this->submitForm($edit, 'Save');
+    $this->drupalGet($nodes[4]->toUrl());
+    // Fetch each node title in the current breadcrumb.
+    $links = $this->xpath('//nav[@aria-labelledby="system-breadcrumb"]/ol/li/a');
+    $got_breadcrumb = [];
+    foreach ($links as $link) {
+      $got_breadcrumb[] = $link->getText();
+    }
+    $this->assertCount(5, $got_breadcrumb);
+    $this->assertEquals($edit['title[0][value]'], end($got_breadcrumb));
+  }
+
+  /**
+   * Tests that the breadcrumb is updated when book access changes.
+   */
+  public function testBreadcrumbAccessUpdates(): void {
+    // Create a new book.
+    $nodes = $this->createBreadcrumbBook();
+    $this->drupalLogin($this->bookAuthor);
+    $edit = [
+      'title[0][value]' => "you can't see me",
+    ];
+    $this->drupalGet($nodes[3]->toUrl('edit-form'));
+    $this->submitForm($edit, 'Save');
+    $this->drupalGet($nodes[4]->toUrl());
+    $links = $this->xpath('//nav[@aria-labelledby="system-breadcrumb"]/ol/li/a');
+    $got_breadcrumb = [];
+    foreach ($links as $link) {
+      $got_breadcrumb[] = $link->getText();
+    }
+    $this->assertCount(5, $got_breadcrumb);
+    $this->assertEquals($edit['title[0][value]'], end($got_breadcrumb));
+    $config = $this->container->get('config.factory')->getEditable('book_breadcrumb_test.settings');
+    $config->set('hide', TRUE)->save();
+    $this->drupalGet($nodes[4]->toUrl());
+    $links = $this->xpath('//nav[@aria-labelledby="system-breadcrumb"]/ol/li/a');
+    $got_breadcrumb = [];
+    foreach ($links as $link) {
+      $got_breadcrumb[] = $link->getText();
+    }
+    $this->assertCount(4, $got_breadcrumb);
+    $this->assertEquals($nodes[2]->getTitle(), end($got_breadcrumb));
+    $this->drupalGet($nodes[3]->toUrl());
+    $this->assertSession()->statusCodeEquals(403);
+  }
+
+}

core/modules/book/tests/src/Functional/BookContentModerationTest.php

@@ -0,0 +1,169 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+use Drupal\Tests\content_moderation\Traits\ContentModerationTestTrait;
+
+/**
+ * Tests Book and Content Moderation integration.
+ *
+ * @group book
+ * @group legacy
+ */
+class BookContentModerationTest extends BrowserTestBase {
+
+  use BookTestTrait;
+  use ContentModerationTestTrait;
+
+  /**
+   * Modules to install.
+   *
+   * @var array
+   */
+  protected static $modules = [
+    'book',
+    'block',
+    'book_test',
+    'content_moderation',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->drupalPlaceBlock('system_breadcrumb_block');
+    $this->drupalPlaceBlock('page_title_block');
+
+    $workflow = $this->createEditorialWorkflow();
+    $workflow->getTypePlugin()->addEntityTypeAndBundle('node', 'book');
+    $workflow->save();
+
+    // We need a user with additional content moderation permissions.
+    $this->bookAuthor = $this->drupalCreateUser([
+      'create new books',
+      'create book content',
+      'edit own book content',
+      'add content to books',
+      'access printer-friendly version',
+      'view any unpublished content',
+      'use editorial transition create_new_draft',
+      'use editorial transition publish',
+    ]);
+  }
+
+  /**
+   * Tests that book drafts can not modify the book outline.
+   */
+  public function testBookWithPendingRevisions(): void {
+    // Create two books.
+    $book_1_nodes = $this->createBook(['moderation_state[0][state]' => 'published']);
+    $book_1 = $this->book;
+
+    $this->createBook(['moderation_state[0][state]' => 'published']);
+    $book_2 = $this->book;
+
+    $this->drupalLogin($this->bookAuthor);
+
+    // Check that book pages display along with the correct outlines.
+    $this->book = $book_1;
+    $this->checkBookNode($book_1, [$book_1_nodes[0], $book_1_nodes[3], $book_1_nodes[4]], FALSE, FALSE, $book_1_nodes[0], []);
+    $this->checkBookNode($book_1_nodes[0], [$book_1_nodes[1], $book_1_nodes[2]], $book_1, $book_1, $book_1_nodes[1], [$book_1]);
+
+    // Create a new book page without actually attaching it to a book and create
+    // a draft.
+    $edit = [
+      'title[0][value]' => $this->randomString(),
+      'moderation_state[0][state]' => 'published',
+    ];
+    $this->drupalGet('node/add/book');
+    $this->submitForm($edit, 'Save');
+    $node = $this->drupalGetNodeByTitle($edit['title[0][value]']);
+    $this->assertNotEmpty($node);
+
+    $edit = [
+      'moderation_state[0][state]' => 'draft',
+    ];
+    $this->drupalGet('node/' . $node->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextNotContains('You can only change the book outline for the published version of this content.');
+
+    // Create a book draft with no changes, then publish it.
+    $edit = [
+      'moderation_state[0][state]' => 'draft',
+    ];
+    $this->drupalGet('node/' . $book_1->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+    $this->assertSession()->pageTextNotContains('You can only change the book outline for the published version of this content.');
+    $edit = [
+      'moderation_state[0][state]' => 'published',
+    ];
+    $this->drupalGet('node/' . $book_1->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+
+    // Try to move Node 2 to a different parent.
+    $edit = [
+      'book[pid]' => $book_1_nodes[3]->id(),
+      'moderation_state[0][state]' => 'draft',
+    ];
+    $this->drupalGet('node/' . $book_1_nodes[1]->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+
+    $this->assertSession()->pageTextContains('You can only change the book outline for the published version of this content.');
+
+    // Check that the book outline did not change.
+    $this->book = $book_1;
+    $this->checkBookNode($book_1, [$book_1_nodes[0], $book_1_nodes[3], $book_1_nodes[4]], FALSE, FALSE, $book_1_nodes[0], []);
+    $this->checkBookNode($book_1_nodes[0], [$book_1_nodes[1], $book_1_nodes[2]], $book_1, $book_1, $book_1_nodes[1], [$book_1]);
+
+    // Try to move Node 2 to a different book.
+    $edit = [
+      'book[bid]' => $book_2->id(),
+      'moderation_state[0][state]' => 'draft',
+    ];
+    $this->drupalGet('node/' . $book_1_nodes[1]->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+
+    $this->assertSession()->pageTextContains('You can only change the book outline for the published version of this content.');
+
+    // Check that the book outline did not change.
+    $this->book = $book_1;
+    $this->checkBookNode($book_1, [$book_1_nodes[0], $book_1_nodes[3], $book_1_nodes[4]], FALSE, FALSE, $book_1_nodes[0], []);
+    $this->checkBookNode($book_1_nodes[0], [$book_1_nodes[1], $book_1_nodes[2]], $book_1, $book_1, $book_1_nodes[1], [$book_1]);
+
+    // Try to change the weight of Node 2.
+    $edit = [
+      'book[weight]' => 2,
+      'moderation_state[0][state]' => 'draft',
+    ];
+    $this->drupalGet('node/' . $book_1_nodes[1]->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+
+    $this->assertSession()->pageTextContains('You can only change the book outline for the published version of this content.');
+
+    // Check that the book outline did not change.
+    $this->book = $book_1;
+    $this->checkBookNode($book_1, [$book_1_nodes[0], $book_1_nodes[3], $book_1_nodes[4]], FALSE, FALSE, $book_1_nodes[0], []);
+    $this->checkBookNode($book_1_nodes[0], [$book_1_nodes[1], $book_1_nodes[2]], $book_1, $book_1, $book_1_nodes[1], [$book_1]);
+
+    // Save a new draft revision for the node without any changes and check that
+    // the error message is not displayed.
+    $edit = [
+      'moderation_state[0][state]' => 'draft',
+    ];
+    $this->drupalGet('node/' . $book_1_nodes[1]->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+
+    $this->assertSession()->pageTextNotContains('You can only change the book outline for the published version of this content.');
+  }
+
+}

core/modules/book/tests/src/Functional/BookTest.php

@@ -0,0 +1,728 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Functional;
+
+use Drupal\Core\Cache\Cache;
+use Drupal\Tests\BrowserTestBase;
+use Drupal\user\RoleInterface;
+
+/**
+ * Create a book, add pages, and test book interface.
+ *
+ * @group book
+ * @group legacy
+ * @group #slow
+ */
+class BookTest extends BrowserTestBase {
+
+  use BookTestTrait;
+
+  /**
+   * Modules to install.
+   *
+   * @var array
+   */
+  protected static $modules = [
+    'content_moderation',
+    'book',
+    'block',
+    'node_access_test',
+    'book_test',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * A user with permission to view a book and access printer-friendly version.
+   *
+   * @var \Drupal\user\UserInterface
+   */
+  protected $webUser;
+
+  /**
+   * A user with permission to create and edit books and to administer blocks.
+   *
+   * @var \Drupal\user\UserInterface
+   */
+  protected $adminUser;
+
+  /**
+   * A user without the 'node test view' permission.
+   *
+   * @var \Drupal\user\UserInterface
+   */
+  protected $webUserWithoutNodeAccess;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->drupalPlaceBlock('system_breadcrumb_block');
+    $this->drupalPlaceBlock('page_title_block');
+
+    // node_access_test requires a node_access_rebuild().
+    node_access_rebuild();
+
+    // Create users.
+    $this->bookAuthor = $this->drupalCreateUser([
+      'create new books',
+      'create book content',
+      'edit own book content',
+      'add content to books',
+      'view own unpublished content',
+    ]);
+    $this->webUser = $this->drupalCreateUser([
+      'access printer-friendly version',
+      'node test view',
+    ]);
+    $this->webUserWithoutNodeAccess = $this->drupalCreateUser([
+      'access printer-friendly version',
+    ]);
+    $this->adminUser = $this->drupalCreateUser([
+      'create new books',
+      'create book content',
+      'edit any book content',
+      'delete any book content',
+      'add content to books',
+      'administer blocks',
+      'administer permissions',
+      'administer book outlines',
+      'node test view',
+      'administer content types',
+      'administer site configuration',
+      'view any unpublished content',
+    ]);
+  }
+
+  /**
+   * Tests the book navigation cache context.
+   *
+   * @see \Drupal\book\Cache\BookNavigationCacheContext
+   */
+  public function testBookNavigationCacheContext(): void {
+    // Create a page node.
+    $this->drupalCreateContentType(['type' => 'page']);
+    $page = $this->drupalCreateNode();
+
+    // Create a book, consisting of book nodes.
+    $book_nodes = $this->createBook();
+
+    // Enable the debug output.
+    \Drupal::state()->set('book_test.debug_book_navigation_cache_context', TRUE);
+    Cache::invalidateTags(['book_test.debug_book_navigation_cache_context']);
+
+    $this->drupalLogin($this->bookAuthor);
+
+    // On non-node route.
+    $this->drupalGet($this->adminUser->toUrl());
+    $this->assertSession()->responseContains('[route.book_navigation]=book.none');
+
+    // On non-book node route.
+    $this->drupalGet($page->toUrl());
+    $this->assertSession()->responseContains('[route.book_navigation]=book.none');
+
+    // On book node route.
+    $this->drupalGet($book_nodes[0]->toUrl());
+    $this->assertSession()->responseContains('[route.book_navigation]=0|2|3');
+    $this->drupalGet($book_nodes[1]->toUrl());
+    $this->assertSession()->responseContains('[route.book_navigation]=0|2|3|4');
+    $this->drupalGet($book_nodes[2]->toUrl());
+    $this->assertSession()->responseContains('[route.book_navigation]=0|2|3|5');
+    $this->drupalGet($book_nodes[3]->toUrl());
+    $this->assertSession()->responseContains('[route.book_navigation]=0|2|6');
+    $this->drupalGet($book_nodes[4]->toUrl());
+    $this->assertSession()->responseContains('[route.book_navigation]=0|2|7');
+  }
+
+  /**
+   * Tests saving the book outline on an empty book.
+   */
+  public function testEmptyBook(): void {
+    // Create a new empty book.
+    $this->drupalLogin($this->bookAuthor);
+    $book = $this->createBookNode('new');
+    $this->drupalLogout();
+
+    // Log in as a user with access to the book outline and save the form.
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet('admin/structure/book/' . $book->id());
+    $this->submitForm([], 'Save book pages');
+    $this->assertSession()->pageTextContains('Updated book ' . $book->label() . '.');
+  }
+
+  /**
+   * Tests book functionality through node interfaces.
+   */
+  public function testBook(): void {
+    // Create new book.
+    $nodes = $this->createBook();
+    $book = $this->book;
+
+    $this->drupalLogin($this->webUser);
+
+    // Check that book pages display along with the correct outlines and
+    // previous/next links.
+    $this->checkBookNode($book, [$nodes[0], $nodes[3], $nodes[4]], FALSE, FALSE, $nodes[0], []);
+    $this->checkBookNode($nodes[0], [$nodes[1], $nodes[2]], $book, $book, $nodes[1], [$book]);
+    $this->checkBookNode($nodes[1], NULL, $nodes[0], $nodes[0], $nodes[2], [$book, $nodes[0]]);
+    $this->checkBookNode($nodes[2], NULL, $nodes[1], $nodes[0], $nodes[3], [$book, $nodes[0]]);
+    $this->checkBookNode($nodes[3], NULL, $nodes[2], $book, $nodes[4], [$book]);
+    $this->checkBookNode($nodes[4], NULL, $nodes[3], $book, FALSE, [$book]);
+
+    $this->drupalLogout();
+    $this->drupalLogin($this->bookAuthor);
+
+    // Check the presence of expected cache tags.
+    $this->drupalGet('node/add/book');
+    $this->assertSession()->responseHeaderContains('X-Drupal-Cache-Tags', 'config:book.settings');
+
+    /*
+     * Add Node 5 under Node 3.
+     * Book
+     *  |- Node 0
+     *   |- Node 1
+     *   |- Node 2
+     *  |- Node 3
+     *   |- Node 5
+     *  |- Node 4
+     */
+    // Node 5.
+    $nodes[] = $this->createBookNode($book->id(), $nodes[3]->book['nid']);
+    $this->drupalLogout();
+    $this->drupalLogin($this->webUser);
+    // Verify the new outline - make sure we don't get stale cached data.
+    $this->checkBookNode($nodes[3], [$nodes[5]], $nodes[2], $book, $nodes[5], [$book]);
+    $this->checkBookNode($nodes[4], NULL, $nodes[5], $book, FALSE, [$book]);
+    $this->drupalLogout();
+    // Create a second book, and move an existing book page into it.
+    $this->drupalLogin($this->bookAuthor);
+    $other_book = $this->createBookNode('new');
+    $node = $this->createBookNode($book->id());
+    $edit = ['book[bid]' => $other_book->id()];
+    $this->drupalGet('node/' . $node->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+
+    $this->drupalLogout();
+    $this->drupalLogin($this->webUser);
+
+    // Check that the nodes in the second book are displayed correctly.
+    // First we must set $this->book to the second book, so that the
+    // correct regex will be generated for testing the outline.
+    $this->book = $other_book;
+    $this->checkBookNode($other_book, [$node], FALSE, FALSE, $node, []);
+    $this->checkBookNode($node, NULL, $other_book, $other_book, FALSE, [$other_book]);
+
+    // Test that we can save a book programmatically.
+    $this->drupalLogin($this->bookAuthor);
+    $book = $this->createBookNode('new');
+    $book->save();
+
+    // Confirm that an unpublished book page has the 'Add child page' link.
+    $this->drupalGet('node/' . $nodes[4]->id());
+    $this->assertSession()->linkExists('Add child page');
+    $nodes[4]->setUnPublished();
+    $nodes[4]->save();
+    $this->drupalGet('node/' . $nodes[4]->id());
+    $this->assertSession()->linkExists('Add child page');
+  }
+
+  /**
+   * Tests book export ("printer-friendly version") functionality.
+   */
+  public function testBookExport(): void {
+    // Create a book.
+    $nodes = $this->createBook();
+
+    // Log in as web user and view printer-friendly version.
+    $this->drupalLogin($this->webUser);
+    $this->drupalGet('node/' . $this->book->id());
+    $this->clickLink('Printer-friendly version');
+
+    // Make sure each part of the book is there.
+    foreach ($nodes as $node) {
+      $this->assertSession()->pageTextContains($node->label());
+      $this->assertSession()->responseContains($node->body->processed);
+    }
+
+    // Make sure we can't export an unsupported format.
+    $this->drupalGet('book/export/foobar/' . $this->book->id());
+    $this->assertSession()->statusCodeEquals(404);
+
+    // Make sure we get a 404 on a non-existent book node.
+    $this->drupalGet('book/export/html/123');
+    $this->assertSession()->statusCodeEquals(404);
+
+    // Make sure an anonymous user cannot view printer-friendly version.
+    $this->drupalLogout();
+
+    // Load the book and verify there is no printer-friendly version link.
+    $this->drupalGet('node/' . $this->book->id());
+    $this->assertSession()->linkNotExists('Printer-friendly version', 'Anonymous user is not shown link to printer-friendly version.');
+
+    // Try getting the URL directly, and verify it fails.
+    $this->drupalGet('book/export/html/' . $this->book->id());
+    $this->assertSession()->statusCodeEquals(403);
+
+    // Now grant anonymous users permission to view the printer-friendly
+    // version and verify that node access restrictions still prevent them from
+    // seeing it.
+    user_role_grant_permissions(RoleInterface::ANONYMOUS_ID, ['access printer-friendly version']);
+    $this->drupalGet('book/export/html/' . $this->book->id());
+    $this->assertSession()->statusCodeEquals(403);
+  }
+
+  /**
+   * Tests the functionality of the book navigation block.
+   */
+  public function testBookNavigationBlock(): void {
+    $this->drupalLogin($this->adminUser);
+
+    // Enable the block.
+    $block = $this->drupalPlaceBlock('book_navigation');
+
+    // Give anonymous users the permission 'node test view'.
+    $edit = [];
+    $edit[RoleInterface::ANONYMOUS_ID . '[node test view]'] = TRUE;
+    $this->drupalGet('admin/people/permissions/' . RoleInterface::ANONYMOUS_ID);
+    $this->submitForm($edit, 'Save permissions');
+    $this->assertSession()->pageTextContains('The changes have been saved.');
+
+    // Test correct display of the block.
+    $nodes = $this->createBook();
+    $this->drupalGet('<front>');
+    // Book navigation block.
+    $this->assertSession()->pageTextContains($block->label());
+    // Link to book root.
+    $this->assertSession()->pageTextContains($this->book->label());
+    // No links to individual book pages.
+    $this->assertSession()->pageTextNotContains($nodes[0]->label());
+
+    // Ensure that an unpublished node does not appear in the navigation for a
+    // user without access. By unpublishing a parent page, child pages should
+    // not appear in the navigation. The node_access_test module is disabled
+    // since it interferes with this logic.
+
+    /** @var \Drupal\Core\Extension\ModuleInstaller $installer */
+    $installer = \Drupal::service('module_installer');
+    $installer->uninstall(['node_access_test']);
+    node_access_rebuild();
+
+    $nodes[0]->setUnPublished();
+    $nodes[0]->save();
+
+    // Verify the user does not have access to the unpublished node.
+    $this->assertFalse($nodes[0]->access('view', $this->webUser));
+
+    // Verify the unpublished book page does not appear in the navigation.
+    $this->drupalLogin($this->webUser);
+    $this->drupalGet($nodes[0]->toUrl());
+    $this->assertSession()->statusCodeEquals(403);
+    $this->drupalGet($this->book->toUrl());
+    $this->assertSession()->responseNotContains($nodes[0]->getTitle());
+    $this->assertSession()->responseNotContains($nodes[1]->getTitle());
+    $this->assertSession()->responseNotContains($nodes[2]->getTitle());
+  }
+
+  /**
+   * Tests BookManager::getTableOfContents().
+   */
+  public function testGetTableOfContents(): void {
+    // Create new book.
+    $nodes = $this->createBook();
+    $book = $this->book;
+
+    $this->drupalLogin($this->bookAuthor);
+
+    /*
+     * Add Node 5 under Node 2.
+     * Add Node 6, 7, 8, 9, 10, 11 under Node 3.
+     * Book
+     *  |- Node 0
+     *   |- Node 1
+     *   |- Node 2
+     *    |- Node 5
+     *  |- Node 3
+     *   |- Node 6
+     *    |- Node 7
+     *     |- Node 8
+     *      |- Node 9
+     *       |- Node 10
+     *        |- Node 11
+     *  |- Node 4
+     */
+    foreach ([5 => 2, 6 => 3, 7 => 6, 8 => 7, 9 => 8, 10 => 9, 11 => 10] as $child => $parent) {
+      $nodes[$child] = $this->createBookNode($book->id(), $nodes[$parent]->id());
+    }
+    $this->drupalGet($nodes[0]->toUrl('edit-form'));
+    // Since Node 0 has children 2 levels deep, nodes 10 and 11 should not
+    // appear in the selector.
+    $this->assertSession()->optionNotExists('edit-book-pid', $nodes[10]->id());
+    $this->assertSession()->optionNotExists('edit-book-pid', $nodes[11]->id());
+    // Node 9 should be available as an option.
+    $this->assertSession()->optionExists('edit-book-pid', $nodes[9]->id());
+
+    // Get a shallow set of options.
+    /** @var \Drupal\book\BookManagerInterface $manager */
+    $manager = $this->container->get('book.manager');
+    $options = $manager->getTableOfContents($book->id(), 3);
+    // Verify that all expected option keys are present.
+    $expected_nids = [$book->id(), $nodes[0]->id(), $nodes[1]->id(), $nodes[2]->id(), $nodes[3]->id(), $nodes[6]->id(), $nodes[4]->id()];
+    $this->assertEquals($expected_nids, array_keys($options));
+    // Exclude Node 3.
+    $options = $manager->getTableOfContents($book->id(), 3, [$nodes[3]->id()]);
+    // Verify that expected option keys are present after excluding Node 3.
+    $expected_nids = [$book->id(), $nodes[0]->id(), $nodes[1]->id(), $nodes[2]->id(), $nodes[4]->id()];
+    $this->assertEquals($expected_nids, array_keys($options));
+  }
+
+  /**
+   * Tests the book navigation block when an access module is installed.
+   */
+  public function testNavigationBlockOnAccessModuleInstalled(): void {
+    $this->drupalLogin($this->adminUser);
+    $block = $this->drupalPlaceBlock('book_navigation', ['block_mode' => 'book pages']);
+
+    // Give anonymous users the permission 'node test view'.
+    $edit = [];
+    $edit[RoleInterface::ANONYMOUS_ID . '[node test view]'] = TRUE;
+    $this->drupalGet('admin/people/permissions/' . RoleInterface::ANONYMOUS_ID);
+    $this->submitForm($edit, 'Save permissions');
+    $this->assertSession()->pageTextContains('The changes have been saved.');
+
+    // Create a book.
+    $this->createBook();
+
+    // Test correct display of the block to registered users.
+    $this->drupalLogin($this->webUser);
+    $this->drupalGet('node/' . $this->book->id());
+    $this->assertSession()->pageTextContains($block->label());
+    $this->drupalLogout();
+
+    // Test correct display of the block to anonymous users.
+    $this->drupalGet('node/' . $this->book->id());
+    $this->assertSession()->pageTextContains($block->label());
+
+    // Test the 'book pages' block_mode setting.
+    $this->drupalGet('<front>');
+    $this->assertSession()->pageTextNotContains($block->label());
+  }
+
+  /**
+   * Tests the access for deleting top-level book nodes.
+   */
+  public function testBookDelete(): void {
+    $node_storage = $this->container->get('entity_type.manager')->getStorage('node');
+    $nodes = $this->createBook();
+    $this->drupalLogin($this->adminUser);
+    $edit = [];
+
+    // Ensure that the top-level book node cannot be deleted.
+    $this->drupalGet('node/' . $this->book->id() . '/outline/remove');
+    $this->assertSession()->statusCodeEquals(403);
+
+    // Ensure that a child book node can be deleted.
+    $this->drupalGet('node/' . $nodes[4]->id() . '/outline/remove');
+    $this->submitForm($edit, 'Remove');
+    $node_storage->resetCache([$nodes[4]->id()]);
+    $node4 = $node_storage->load($nodes[4]->id());
+    $this->assertEmpty($node4->book, 'Deleting child book node properly allowed.');
+
+    // $nodes[4] is stale, trying to delete it directly will cause an error.
+    $node4->delete();
+    unset($nodes[4]);
+
+    // Delete all child book nodes and retest top-level node deletion.
+    $node_storage->delete($nodes);
+
+    $this->drupalGet('node/' . $this->book->id() . '/outline/remove');
+    $this->submitForm($edit, 'Remove');
+    $node_storage->resetCache([$this->book->id()]);
+    $node = $node_storage->load($this->book->id());
+    $this->assertEmpty($node->book, 'Deleting childless top-level book node properly allowed.');
+
+    // Tests directly deleting a book parent.
+    $nodes = $this->createBook();
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet($this->book->toUrl('delete-form'));
+    $this->assertSession()->pageTextContains($this->book->label() . ' is part of a book outline, and has associated child pages. If you proceed with deletion, the child pages will be relocated automatically.');
+    // Delete parent, and visit a child page.
+    $this->drupalGet($this->book->toUrl('delete-form'));
+    $this->submitForm([], 'Delete');
+    $this->drupalGet($nodes[0]->toUrl());
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSession()->pageTextContains($nodes[0]->label());
+    // The book parents should be updated.
+    $node_storage = \Drupal::entityTypeManager()->getStorage('node');
+    $node_storage->resetCache();
+    $child = $node_storage->load($nodes[0]->id());
+    $this->assertEquals($child->id(), $child->book['bid'], 'Child node book ID updated when parent is deleted.');
+    // 3rd-level children should now be 2nd-level.
+    $second = $node_storage->load($nodes[1]->id());
+    $this->assertEquals($child->id(), $second->book['bid'], '3rd-level child node is now second level when top-level node is deleted.');
+  }
+
+  /**
+   * Tests outline of a book.
+   */
+  public function testBookOutline(): void {
+    $this->drupalLogin($this->bookAuthor);
+
+    // Create new node not yet a book.
+    $empty_book = $this->drupalCreateNode(['type' => 'book']);
+    $this->drupalGet('node/' . $empty_book->id() . '/outline');
+    $this->assertSession()->linkNotExists('Book outline', 'Book Author is not allowed to outline');
+
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet('node/' . $empty_book->id() . '/outline');
+    $this->assertSession()->pageTextContains('Book outline');
+    // Verify that the node does not belong to a book.
+    $this->assertTrue($this->assertSession()->optionExists('edit-book-bid', 0)->isSelected());
+    $this->assertSession()->linkNotExists('Remove from book outline');
+
+    $edit = [];
+    $edit['book[bid]'] = '1';
+    $this->drupalGet('node/' . $empty_book->id() . '/outline');
+    $this->submitForm($edit, 'Add to book outline');
+    $node = \Drupal::entityTypeManager()->getStorage('node')->load($empty_book->id());
+    // Test the book array.
+    $this->assertEquals($empty_book->id(), $node->book['nid']);
+    $this->assertEquals($empty_book->id(), $node->book['bid']);
+    $this->assertEquals(1, $node->book['depth']);
+    $this->assertEquals($empty_book->id(), $node->book['p1']);
+    $this->assertEquals('0', $node->book['pid']);
+
+    // Create new book.
+    $this->drupalLogin($this->bookAuthor);
+    $book = $this->createBookNode('new');
+
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet('node/' . $book->id() . '/outline');
+    $this->assertSession()->pageTextContains('Book outline');
+    $this->clickLink('Remove from book outline');
+    $this->assertSession()->pageTextContains('Are you sure you want to remove ' . $book->label() . ' from the book hierarchy?');
+
+    // Create a new node and set the book after the node was created.
+    $node = $this->drupalCreateNode(['type' => 'book']);
+    $edit = [];
+    $edit['book[bid]'] = $node->id();
+    $this->drupalGet('node/' . $node->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+    $node = \Drupal::entityTypeManager()->getStorage('node')->load($node->id());
+
+    // Test the book array.
+    $this->assertEquals($node->id(), $node->book['nid']);
+    $this->assertEquals($node->id(), $node->book['bid']);
+    $this->assertEquals(1, $node->book['depth']);
+    $this->assertEquals($node->id(), $node->book['p1']);
+    $this->assertEquals('0', $node->book['pid']);
+
+    // Test the form itself.
+    $this->drupalGet('node/' . $node->id() . '/edit');
+    $this->assertTrue($this->assertSession()->optionExists('edit-book-bid', $node->id())->isSelected());
+  }
+
+  /**
+   * Tests that saveBookLink() returns something.
+   */
+  public function testSaveBookLink(): void {
+    $book_manager = \Drupal::service('book.manager');
+
+    // Mock a link for a new book.
+    $link = ['nid' => 1, 'has_children' => 0, 'original_bid' => 0, 'pid' => 0, 'weight' => 0, 'bid' => 0];
+    $new = TRUE;
+
+    // Save the link.
+    $return = $book_manager->saveBookLink($link, $new);
+
+    // Add the link defaults to $link so we have something to compare to the return from saveBookLink().
+    $link = $book_manager->getLinkDefaults($link['nid']);
+
+    // Test the return from saveBookLink.
+    $this->assertEquals($return, $link);
+  }
+
+  /**
+   * Tests the listing of all books.
+   */
+  public function testBookListing(): void {
+    // Uninstall 'node_access_test' as this interferes with the test.
+    \Drupal::service('module_installer')->uninstall(['node_access_test']);
+
+    // Create a new book.
+    $nodes = $this->createBook();
+
+    // Load the book page and assert the created book title is displayed.
+    $this->drupalGet('book');
+    $this->assertSession()->pageTextContains($this->book->label());
+
+    // Unpublish the top book page and confirm that the created book title is
+    // not displayed for anonymous.
+    $this->book->setUnpublished();
+    $this->book->save();
+
+    $this->drupalGet('book');
+    $this->assertSession()->pageTextNotContains($this->book->label());
+
+    // Publish the top book page and unpublish a page in the book and confirm
+    // that the created book title is displayed for anonymous.
+    $this->book->setPublished();
+    $this->book->save();
+    $nodes[0]->setUnpublished();
+    $nodes[0]->save();
+
+    $this->drupalGet('book');
+    $this->assertSession()->pageTextContains($this->book->label());
+
+    // Unpublish the top book page and confirm that the created book title is
+    // displayed for user which has 'view own unpublished content' permission.
+    $this->drupalLogin($this->bookAuthor);
+    $this->book->setUnpublished();
+    $this->book->save();
+
+    $this->drupalGet('book');
+    $this->assertSession()->pageTextContains($this->book->label());
+
+    // Ensure the user doesn't see the book if they don't own it.
+    $this->book->setOwner($this->webUser)->save();
+    $this->drupalGet('book');
+    $this->assertSession()->pageTextNotContains($this->book->label());
+
+    // Confirm that the created book title is displayed for user which has
+    // 'view any unpublished content' permission.
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet('book');
+    $this->assertSession()->pageTextContains($this->book->label());
+  }
+
+  /**
+   * Tests the administrative listing of all books.
+   */
+  public function testAdminBookListing(): void {
+    // Create a new book.
+    $nodes = $this->createBook();
+
+    // Load the book page and assert the created book title is displayed.
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet('admin/structure/book');
+    $this->assertSession()->pageTextContains($this->book->label());
+  }
+
+  /**
+   * Tests the administrative listing of all book pages in a book.
+   */
+  public function testAdminBookNodeListing(): void {
+    // Create a new book.
+    $nodes = $this->createBook();
+    $this->drupalLogin($this->adminUser);
+
+    // Load the book page list and assert the created book title is displayed
+    // and action links are shown on list items.
+    $this->drupalGet('admin/structure/book/' . $this->book->id());
+    $this->assertSession()->pageTextContains($this->book->label());
+
+    // Test that the view link is found from the list.
+    $this->assertSession()->elementTextEquals('xpath', '//table//ul[@class="dropbutton"]/li/a', 'View');
+
+    // Test that all the book pages are displayed on the book outline page.
+    $this->assertSession()->elementsCount('xpath', '//table//ul[@class="dropbutton"]/li/a', count($nodes));
+
+    // Unpublish a book in the hierarchy.
+    $nodes[0]->setUnPublished();
+    $nodes[0]->save();
+
+    // Node should still appear on the outline for admins.
+    $this->drupalGet('admin/structure/book/' . $this->book->id());
+    $this->assertSession()->elementsCount('xpath', '//table//ul[@class="dropbutton"]/li/a', count($nodes));
+
+    // Saving a book page not as the current version shouldn't effect the book.
+    $old_title = $nodes[1]->getTitle();
+    $new_title = $this->getRandomGenerator()->name();
+    $nodes[1]->isDefaultRevision(FALSE);
+    $nodes[1]->setNewRevision(TRUE);
+    $nodes[1]->setTitle($new_title);
+    $nodes[1]->save();
+    $this->drupalGet('admin/structure/book/' . $this->book->id());
+    $this->assertSession()->elementsCount('xpath', '//table//ul[@class="dropbutton"]/li/a', count($nodes));
+    $this->assertSession()->responseNotContains($new_title);
+    $this->assertSession()->responseContains($old_title);
+  }
+
+  /**
+   * Ensure the loaded book in hook_node_load() does not depend on the user.
+   */
+  public function testHookNodeLoadAccess(): void {
+    \Drupal::service('module_installer')->install(['node_access_test']);
+
+    // Ensure that the loaded book in hook_node_load() does NOT depend on the
+    // current user.
+    $this->drupalLogin($this->bookAuthor);
+    $this->book = $this->createBookNode('new');
+    // Reset any internal static caching.
+    $node_storage = \Drupal::entityTypeManager()->getStorage('node');
+    $node_storage->resetCache();
+
+    // Log in as user without access to the book node, so no 'node test view'
+    // permission.
+    // @see node_access_test_node_grants().
+    $this->drupalLogin($this->webUserWithoutNodeAccess);
+    $book_node = $node_storage->load($this->book->id());
+    $this->assertNotEmpty($book_node->book);
+    $this->assertEquals($this->book->id(), $book_node->book['bid']);
+
+    // Reset the internal cache to retrigger the hook_node_load() call.
+    $node_storage->resetCache();
+
+    $this->drupalLogin($this->webUser);
+    $book_node = $node_storage->load($this->book->id());
+    $this->assertNotEmpty($book_node->book);
+    $this->assertEquals($this->book->id(), $book_node->book['bid']);
+  }
+
+  /**
+   * Tests the book navigation block when book is unpublished.
+   *
+   * There was a fatal error with "Show block only on book pages" block mode.
+   */
+  public function testBookNavigationBlockOnUnpublishedBook(): void {
+    // Create a new book.
+    $this->createBook();
+
+    // Create administrator user.
+    $administratorUser = $this->drupalCreateUser([
+      'administer blocks',
+      'administer nodes',
+      'bypass node access',
+    ]);
+    $this->drupalLogin($administratorUser);
+
+    // Enable the block with "Show block only on book pages" mode.
+    $this->drupalPlaceBlock('book_navigation', ['block_mode' => 'book pages']);
+
+    // Unpublish book node.
+    $edit = ['status[value]' => FALSE];
+    $this->drupalGet('node/' . $this->book->id() . '/edit');
+    $this->submitForm($edit, 'Save');
+
+    // Test node page.
+    $this->drupalGet('node/' . $this->book->id());
+    // Unpublished book with "Show block only on book pages" book navigation
+    // settings.
+    $this->assertSession()->pageTextContains($this->book->label());
+  }
+
+  /**
+   * Tests that the book settings form can be saved without error.
+   */
+  public function testSettingsForm(): void {
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet('admin/structure/book/settings');
+    $this->submitForm([], 'Save configuration');
+  }
+
+}

core/modules/book/tests/src/Functional/BookTestTrait.php

@@ -0,0 +1,224 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Functional;
+
+use Drupal\Core\Url;
+use Drupal\Core\Entity\EntityInterface;
+
+/**
+ * Provides common functionality for Book test classes.
+ */
+trait BookTestTrait {
+
+  /**
+   * A book node.
+   *
+   * @var \Drupal\node\NodeInterface
+   */
+  protected $book;
+
+  /**
+   * A user with permission to create and edit books.
+   *
+   * @var \Drupal\Core\Session\AccountInterface
+   */
+  protected $bookAuthor;
+
+  /**
+   * Creates a new book with a page hierarchy.
+   *
+   * @param array $edit
+   *   (optional) Field data in an associative array. Changes the current input
+   *   fields (where possible) to the values indicated. Defaults to an empty
+   *   array.
+   *
+   * @return \Drupal\node\NodeInterface[]
+   */
+  public function createBook($edit = []) {
+    // Create new book.
+    $this->drupalLogin($this->bookAuthor);
+
+    $this->book = $this->createBookNode('new', NULL, $edit);
+    $book = $this->book;
+
+    /*
+     * Add page hierarchy to book.
+     * Book
+     *  |- Node 0
+     *   |- Node 1
+     *   |- Node 2
+     *  |- Node 3
+     *  |- Node 4
+     */
+    $nodes = [];
+    // Node 0.
+    $nodes[] = $this->createBookNode($book->id(), NULL, $edit);
+    // Node 1.
+    $nodes[] = $this->createBookNode($book->id(), $nodes[0]->book['nid'], $edit);
+    // Node 2.
+    $nodes[] = $this->createBookNode($book->id(), $nodes[0]->book['nid'], $edit);
+    // Node 3.
+    $nodes[] = $this->createBookNode($book->id(), NULL, $edit);
+    // Node 4.
+    $nodes[] = $this->createBookNode($book->id(), NULL, $edit);
+
+    $this->drupalLogout();
+
+    return $nodes;
+  }
+
+  /**
+   * Checks the outline of sub-pages; previous, up, and next.
+   *
+   * Also checks the printer friendly version of the outline.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface $node
+   *   Node to check.
+   * @param $nodes
+   *   Nodes that should be in outline.
+   * @param $previous
+   *   Previous link node.
+   * @param $up
+   *   Up link node.
+   * @param $next
+   *   Next link node.
+   * @param array $breadcrumb
+   *   The nodes that should be displayed in the breadcrumb.
+   */
+  public function checkBookNode(EntityInterface $node, $nodes, $previous, $up, $next, array $breadcrumb) {
+    $this->drupalGet('node/' . $node->id());
+    // Check outline structure.
+    if ($nodes !== NULL) {
+      $book_navigation = $this->getSession()->getPage()->find('css', sprintf('nav[aria-labelledby="book-label-%s"] ul', $this->book->id()));
+      $this->assertNotNull($book_navigation);
+      $links = $book_navigation->findAll('css', 'a');
+      $this->assertCount(count($nodes), $links);
+      foreach ($nodes as $delta => $node) {
+        $link = $links[$delta];
+        $this->assertEquals($node->label(), $link->getText());
+        $this->assertEquals($node->toUrl()->toString(), $link->getAttribute('href'));
+      }
+    }
+
+    // Check previous, up, and next links.
+    if ($previous) {
+      $previous_element = $this->assertSession()->elementExists('named_exact', [
+        'link',
+        'Go to previous page',
+      ]);
+      $this->assertEquals($previous->toUrl()->toString(), $previous_element->getAttribute('href'));
+    }
+
+    if ($up) {
+      $parent_element = $this->assertSession()->elementExists('named_exact', [
+        'link',
+        'Go to parent page',
+      ]);
+      $this->assertEquals($up->toUrl()->toString(), $parent_element->getAttribute('href'));
+    }
+
+    if ($next) {
+      $next_element = $this->assertSession()->elementExists('named_exact', [
+        'link',
+        'Go to next page',
+      ]);
+      $this->assertEquals($next->toUrl()->toString(), $next_element->getAttribute('href'));
+    }
+
+    // Compute the expected breadcrumb.
+    $expected_breadcrumb = [];
+    $expected_breadcrumb[] = Url::fromRoute('<front>')->toString();
+    foreach ($breadcrumb as $a_node) {
+      $expected_breadcrumb[] = $a_node->toUrl()->toString();
+    }
+
+    // Fetch links in the current breadcrumb.
+    $links = $this->xpath('//nav[@aria-labelledby="system-breadcrumb"]/ol/li/a');
+    $got_breadcrumb = [];
+    foreach ($links as $link) {
+      $got_breadcrumb[] = $link->getAttribute('href');
+    }
+
+    // Compare expected and got breadcrumbs.
+    $this->assertSame($expected_breadcrumb, $got_breadcrumb, 'The breadcrumb is correctly displayed on the page.');
+
+    // Check printer friendly version.
+    $this->drupalGet('book/export/html/' . $node->id());
+    $this->assertSession()->pageTextContains($node->label());
+    $this->assertSession()->responseContains($node->body->processed);
+  }
+
+  /**
+   * Creates a regular expression to check for the sub-nodes in the outline.
+   *
+   * @param array $nodes
+   *   An array of nodes to check in outline.
+   *
+   * @return string
+   *   A regular expression that locates sub-nodes of the outline.
+   *
+   * @deprecated in drupal:10.1.0 and is removed from drupal:11.0.0. Use
+   *   methods from \Drupal\Tests\WebAssert instead.
+   *
+   * @see https://www.drupal.org/node/3325904
+   */
+  public function generateOutlinePattern($nodes) {
+    @trigger_error(__METHOD__ . ' is deprecated in drupal:10.1.0 and is removed from drupal:11.0.0. Use methods from \Drupal\Tests\WebAssert instead. See https://www.drupal.org/node/3325904', E_USER_DEPRECATED);
+    $outline = '';
+    foreach ($nodes as $node) {
+      $outline .= '(node\/' . $node->id() . ')(.*?)(' . $node->label() . ')(.*?)';
+    }
+    return '/<nav role="navigation" aria-labelledby="book-label-' . $this->book->id() . '"(.*?)<ul(.*?)' . $outline . '<\/ul>/s';
+  }
+
+  /**
+   * Creates a book node.
+   *
+   * @param int|string $book_nid
+   *   A book node ID or set to 'new' to create a new book.
+   * @param int|null $parent
+   *   (optional) Parent book reference ID. Defaults to NULL.
+   * @param array $edit
+   *   (optional) Field data in an associative array. Changes the current input
+   *   fields (where possible) to the values indicated. Defaults to an empty
+   *   array.
+   *
+   * @return \Drupal\node\NodeInterface
+   *   The created node.
+   */
+  public function createBookNode($book_nid, $parent = NULL, $edit = []) {
+    // $number does not use drupal_static as it should not be reset
+    // since it uniquely identifies each call to createBookNode().
+    // Used to ensure that when sorted nodes stay in same order.
+    static $number = 0;
+
+    $edit['title[0][value]'] = str_pad((string) $number, 2, '0', STR_PAD_LEFT) . ' - test node ' . $this->randomMachineName(10);
+    $edit['body[0][value]'] = 'test body ' . $this->randomMachineName(32) . ' ' . $this->randomMachineName(32);
+    $edit['book[bid]'] = $book_nid;
+
+    if ($parent !== NULL) {
+      $this->drupalGet('node/add/book');
+      $this->submitForm($edit, 'Change book (update list of parents)');
+
+      $edit['book[pid]'] = $parent;
+      $this->submitForm($edit, 'Save');
+      // Make sure the parent was flagged as having children.
+      $parent_node = \Drupal::entityTypeManager()->getStorage('node')->loadUnchanged($parent);
+      $this->assertNotEmpty($parent_node->book['has_children'], 'Parent node is marked as having children');
+    }
+    else {
+      $this->drupalGet('node/add/book');
+      $this->submitForm($edit, 'Save');
+    }
+
+    // Check to make sure the book node was created.
+    $node = $this->drupalGetNodeByTitle($edit['title[0][value]']);
+    $this->assertNotNull(($node === FALSE ? NULL : $node), 'Book node found in database.');
+    $number++;
+
+    return $node;
+  }
+
+}

core/modules/book/tests/src/Functional/Comment/CommentBookTest.php

@@ -0,0 +1,95 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Functional\Comment;
+
+use Drupal\comment\CommentInterface;
+use Drupal\comment\Tests\CommentTestTrait;
+use Drupal\node\Entity\Node;
+use Drupal\Tests\BrowserTestBase;
+use Drupal\comment\Entity\Comment;
+
+/**
+ * Tests visibility of comments on book pages.
+ *
+ * @group book
+ * @group legacy
+ */
+class CommentBookTest extends BrowserTestBase {
+
+  use CommentTestTrait;
+
+  /**
+   * Modules to install.
+   *
+   * @var array
+   */
+  protected static $modules = ['book', 'comment'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    // Create comment field on book.
+    $this->addDefaultCommentField('node', 'book');
+  }
+
+  /**
+   * Tests comments in book export.
+   */
+  public function testBookCommentPrint(): void {
+    $book_node = Node::create([
+      'type' => 'book',
+      'title' => 'Book title',
+      'body' => 'Book body',
+    ]);
+    $book_node->book['bid'] = 'new';
+    $book_node->save();
+
+    $comment_subject = $this->randomMachineName(8);
+    $comment_body = $this->randomMachineName(8);
+    $comment = Comment::create([
+      'subject' => $comment_subject,
+      'comment_body' => $comment_body,
+      'entity_id' => $book_node->id(),
+      'entity_type' => 'node',
+      'field_name' => 'comment',
+      'status' => CommentInterface::PUBLISHED,
+    ]);
+    $comment->save();
+
+    $commenting_user = $this->drupalCreateUser([
+      'access printer-friendly version',
+      'access comments',
+      'post comments',
+    ]);
+    $this->drupalLogin($commenting_user);
+
+    $this->drupalGet('node/' . $book_node->id());
+
+    $this->assertSession()->pageTextContains($comment_subject);
+    $this->assertSession()->pageTextContains($comment_body);
+    $this->assertSession()->pageTextContains('Add new comment');
+    // Ensure that the comment form subject field exists.
+    $this->assertSession()->fieldExists('subject[0][value]');
+
+    $this->drupalGet('book/export/html/' . $book_node->id());
+
+    $this->assertSession()->pageTextContains('Comments');
+    $this->assertSession()->pageTextContains($comment_subject);
+    $this->assertSession()->pageTextContains($comment_body);
+
+    $this->assertSession()->pageTextNotContains('Add new comment');
+    // Verify that the comment form subject field is not found.
+    $this->assertSession()->fieldNotExists('subject[0][value]');
+  }
+
+}

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

@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Functional;
+
+use Drupal\Tests\system\Functional\Module\GenericModuleTestBase;
+
+/**
+ * Generic module test for book.
+ *
+ * @group book
+ * @group legacy
+ */
+class GenericTest extends GenericModuleTestBase {}

core/modules/book/tests/src/Functional/Migrate/d6/ReviewPageTest.php

@@ -0,0 +1,75 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Functional\Migrate\d6;
+
+use Drupal\Tests\migrate_drupal_ui\Functional\NoMultilingualReviewPageTestBase;
+
+/**
+ * Tests Review page.
+ *
+ * @group book
+ * @group legacy
+ */
+class ReviewPageTest extends NoMultilingualReviewPageTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['book'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->loadFixture($this->getModulePath('book') . '/tests/fixtures/drupal6.php');
+  }
+
+  /**
+   * Tests the review page.
+   */
+  public function testMigrateUpgradeReviewPage(): void {
+    $this->prepare();
+    // Start the upgrade process.
+    $this->submitCredentialForm();
+
+    $session = $this->assertSession();
+    $this->submitForm([], 'I acknowledge I may lose data. Continue anyway.');
+    $session->statusCodeEquals(200);
+
+    // Confirm that Book will be upgraded.
+    $session->elementExists('xpath', "//td[contains(@class, 'checked') and text() = 'Book']");
+    $session->elementNotExists('xpath', "//td[contains(@class, 'error') and text() = 'Book']");
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getSourceBasePath() {
+    return __DIR__;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getAvailablePaths() {
+    return [];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getIncompletePaths() {
+    return [];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getMissingPaths() {
+    return [];
+  }
+
+}

core/modules/book/tests/src/Functional/Migrate/d7/ReviewPageTest.php

@@ -0,0 +1,75 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Functional\Migrate\d7;
+
+use Drupal\Tests\migrate_drupal_ui\Functional\NoMultilingualReviewPageTestBase;
+
+/**
+ * Tests Review page.
+ *
+ * @group book
+ * @group legacy
+ */
+class ReviewPageTest extends NoMultilingualReviewPageTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['book'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->loadFixture($this->getModulePath('book') . '/tests/fixtures/drupal7.php');
+  }
+
+  /**
+   * Tests the review page.
+   */
+  public function testMigrateUpgradeReviewPage(): void {
+    $this->prepare();
+    // Start the upgrade process.
+    $this->submitCredentialForm();
+
+    $session = $this->assertSession();
+    $this->submitForm([], 'I acknowledge I may lose data. Continue anyway.');
+    $session->statusCodeEquals(200);
+
+    // Confirm that Book will be upgraded.
+    $session->elementExists('xpath', "//td[contains(@class, 'checked') and text() = 'Book']");
+    $session->elementNotExists('xpath', "//td[contains(@class, 'error') and text() = 'Book']");
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getSourceBasePath() {
+    return __DIR__;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getAvailablePaths() {
+    return [];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getIncompletePaths() {
+    return [];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getMissingPaths() {
+    return [];
+  }
+
+}

core/modules/book/tests/src/Functional/Views/BookRelationshipTest.php

@@ -0,0 +1,166 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Functional\Views;
+
+use Drupal\Tests\views\Functional\ViewTestBase;
+use Drupal\views\Tests\ViewTestData;
+
+/**
+ * Tests entity reference relationship data.
+ *
+ * @group book
+ * @group legacy
+ *
+ * @see book_views_data()
+ */
+class BookRelationshipTest extends ViewTestBase {
+
+  /**
+   * Views used by this test.
+   *
+   * @var array
+   */
+  public static $testViews = ['test_book_view'];
+
+  /**
+   * Modules to install.
+   *
+   * @var array
+   */
+  protected static $modules = ['book_test_views', 'book', 'views'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * A book node.
+   *
+   * @var object
+   */
+  protected $book;
+
+  /**
+   * A user with permission to create and edit books.
+   *
+   * @var object
+   */
+  protected $bookAuthor;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp($import_test_views = TRUE, $modules = []): void {
+    parent::setUp($import_test_views, $modules);
+
+    // Create users.
+    $this->bookAuthor = $this->drupalCreateUser(
+      [
+        'create new books',
+        'create book content',
+        'edit own book content',
+        'add content to books',
+      ]
+    );
+    ViewTestData::createTestViews(static::class, ['book_test_views']);
+  }
+
+  /**
+   * Creates a new book with a page hierarchy.
+   */
+  protected function createBook() {
+    // Create new book.
+    $this->drupalLogin($this->bookAuthor);
+
+    $this->book = $this->createBookNode('new');
+    $book = $this->book;
+
+    $nodes = [];
+    // Node 0.
+    $nodes[] = $this->createBookNode($book->id());
+    // Node 1.
+    $nodes[] = $this->createBookNode($book->id(), $nodes[0]->book['nid']);
+    // Node 2.
+    $nodes[] = $this->createBookNode($book->id(), $nodes[1]->book['nid']);
+    // Node 3.
+    $nodes[] = $this->createBookNode($book->id(), $nodes[2]->book['nid']);
+    // Node 4.
+    $nodes[] = $this->createBookNode($book->id(), $nodes[3]->book['nid']);
+    // Node 5.
+    $nodes[] = $this->createBookNode($book->id(), $nodes[4]->book['nid']);
+    // Node 6.
+    $nodes[] = $this->createBookNode($book->id(), $nodes[5]->book['nid']);
+    // Node 7.
+    $nodes[] = $this->createBookNode($book->id(), $nodes[6]->book['nid']);
+
+    $this->drupalLogout();
+
+    return $nodes;
+  }
+
+  /**
+   * Creates a book node.
+   *
+   * @param int|string $book_nid
+   *   A book node ID or set to 'new' to create a new book.
+   * @param int|null $parent
+   *   (optional) Parent book reference ID. Defaults to NULL.
+   *
+   * @return \Drupal\node\NodeInterface
+   *   The book node.
+   */
+  protected function createBookNode($book_nid, $parent = NULL) {
+    // $number does not use drupal_static as it should not be reset
+    // since it uniquely identifies each call to createBookNode().
+    // Used to ensure that when sorted nodes stay in same order.
+    static $number = 0;
+
+    $edit = [];
+    $edit['title[0][value]'] = $number . ' - test node ' . $this->randomMachineName(10);
+    $edit['body[0][value]'] = 'test body ' . $this->randomMachineName(32) . ' ' . $this->randomMachineName(32);
+    $edit['book[bid]'] = $book_nid;
+
+    if ($parent !== NULL) {
+      $this->drupalGet('node/add/book');
+      $this->submitForm($edit, 'Change book (update list of parents)');
+
+      $edit['book[pid]'] = $parent;
+      $this->submitForm($edit, 'Save');
+      // Make sure the parent was flagged as having children.
+      $parent_node = \Drupal::entityTypeManager()->getStorage('node')->loadUnchanged($parent);
+      $this->assertNotEmpty($parent_node->book['has_children'], 'Parent node is marked as having children');
+    }
+    else {
+      $this->drupalGet('node/add/book');
+      $this->submitForm($edit, 'Save');
+    }
+
+    // Check to make sure the book node was created.
+    $node = $this->drupalGetNodeByTitle($edit['title[0][value]']);
+    $this->assertNotNull(($node === FALSE ? NULL : $node), 'Book node found in database.');
+    $number++;
+
+    return $node;
+  }
+
+  /**
+   * Tests using the views relationship.
+   */
+  public function testRelationship(): void {
+
+    // Create new book.
+    /** @var \Drupal\node\NodeInterface[] $nodes */
+    $nodes = $this->createBook();
+    for ($i = 0; $i < 8; $i++) {
+      $this->drupalGet('test-book/' . $nodes[$i]->id());
+
+      for ($j = 0; $j < $i; $j++) {
+        $this->assertSession()->linkExists($nodes[$j]->label());
+      }
+    }
+  }
+
+}

core/modules/book/tests/src/FunctionalJavascript/BookJavascriptTest.php

@@ -0,0 +1,192 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\FunctionalJavascript;
+
+use Behat\Mink\Exception\ExpectationException;
+use Drupal\Component\Render\FormattableMarkup;
+use Drupal\FunctionalJavascriptTests\WebDriverTestBase;
+use Drupal\node\Entity\Node;
+
+/**
+ * Tests Book javascript functionality.
+ *
+ * @group book
+ * @group legacy
+ */
+class BookJavascriptTest extends WebDriverTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['book'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Tests re-ordering of books.
+   */
+  public function testBookOrdering(): void {
+    $book = Node::create([
+      'type' => 'book',
+      'title' => 'Book',
+      'book' => ['bid' => 'new'],
+    ]);
+    $book->save();
+    $page1 = Node::create([
+      'type' => 'book',
+      'title' => '1st page',
+      'book' => ['bid' => $book->id(), 'pid' => $book->id(), 'weight' => 0],
+    ]);
+    $page1->save();
+    $page2 = Node::create([
+      'type' => 'book',
+      'title' => '2nd page',
+      'book' => ['bid' => $book->id(), 'pid' => $book->id(), 'weight' => 1],
+    ]);
+    $page2->save();
+
+    // Head to admin screen and attempt to re-order.
+    $this->drupalLogin($this->drupalCreateUser(['administer book outlines']));
+    $this->drupalGet('admin/structure/book/' . $book->id());
+
+    $page = $this->getSession()->getPage();
+
+    $weight_select1 = $page->findField("table[book-admin-{$page1->id()}][weight]");
+    $weight_select2 = $page->findField("table[book-admin-{$page2->id()}][weight]");
+
+    // Check that rows weight selects are hidden.
+    $this->assertFalse($weight_select1->isVisible());
+    $this->assertFalse($weight_select2->isVisible());
+
+    // Check that '2nd page' row is heavier than '1st page' row.
+    $this->assertGreaterThan($weight_select1->getValue(), $weight_select2->getValue());
+
+    // Check that '1st page' precedes the '2nd page'.
+    $this->assertOrderInPage(['1st page', '2nd page']);
+
+    // Check that the 'unsaved changes' text is not present in the message area.
+    $this->assertSession()->pageTextNotContains('You have unsaved changes.');
+
+    // Drag and drop the '1st page' row over the '2nd page' row.
+    // @todo Test also the reverse, '2nd page' over '1st page', when
+    //   https://www.drupal.org/node/2769825 is fixed.
+    // @see https://www.drupal.org/node/2769825
+    $dragged = $this->xpath("//tr[@data-drupal-selector='edit-table-book-admin-{$page1->id()}']//a[@class='tabledrag-handle']")[0];
+    $target = $this->xpath("//tr[@data-drupal-selector='edit-table-book-admin-{$page2->id()}']//a[@class='tabledrag-handle']")[0];
+    $dragged->dragTo($target);
+
+    // Give javascript some time to manipulate the DOM.
+    $this->assertJsCondition('jQuery(".tabledrag-changed-warning").is(":visible")');
+
+    // Check that the 'unsaved changes' text appeared in the message area.
+    $this->assertSession()->pageTextContains('You have unsaved changes.');
+
+    // Check that '2nd page' page precedes the '1st page'.
+    $this->assertOrderInPage(['2nd page', '1st page']);
+
+    $this->submitForm([], 'Save book pages');
+    $this->assertSession()->pageTextContains(new FormattableMarkup('Updated book @book.', ['@book' => $book->getTitle()]));
+
+    // Check that page reordering was done in the backend for drag-n-drop.
+    $page1 = Node::load($page1->id());
+    $page2 = Node::load($page2->id());
+    $this->assertGreaterThan($page2->book['weight'], $page1->book['weight']);
+
+    // Check again that '2nd page' is on top after form submit in the UI.
+    $this->assertOrderInPage(['2nd page', '1st page']);
+
+    // Toggle row weight selects as visible.
+    $page->findButton('Show row weights')->click();
+
+    // Check that rows weight selects are visible.
+    $this->assertTrue($weight_select1->isVisible());
+    $this->assertTrue($weight_select2->isVisible());
+
+    // Check that '1st page' row became heavier than '2nd page' row.
+    $this->assertGreaterThan($weight_select2->getValue(), $weight_select1->getValue());
+
+    // Reverse again using the weight fields. Use the current values so the test
+    // doesn't rely on knowing the values in the select boxes.
+    $value1 = $weight_select1->getValue();
+    $value2 = $weight_select2->getValue();
+    $weight_select1->setValue($value2);
+    $weight_select2->setValue($value1);
+
+    // Toggle row weight selects back to hidden.
+    $page->findButton('Hide row weights')->click();
+
+    // Check that rows weight selects are hidden again.
+    $this->assertFalse($weight_select1->isVisible());
+    $this->assertFalse($weight_select2->isVisible());
+
+    $this->submitForm([], 'Save book pages');
+    $this->assertSession()->pageTextContains(new FormattableMarkup('Updated book @book.', ['@book' => $book->getTitle()]));
+
+    // Check that the '1st page' is first again.
+    $this->assertOrderInPage(['1st page', '2nd page']);
+
+    // Check that page reordering was done in the backend for manual weight
+    // field usage.
+    $page1 = Node::load($page1->id());
+    $page2 = Node::load($page2->id());
+    $this->assertGreaterThan($page2->book['weight'], $page1->book['weight']);
+  }
+
+  /**
+   * Asserts that several pieces of markup are in a given order in the page.
+   *
+   * @param string[] $items
+   *   An ordered list of strings.
+   *
+   * @throws \Behat\Mink\Exception\ExpectationException
+   *   When any of the given string is not found.
+   *
+   * @internal
+   *
+   * @todo Remove this once https://www.drupal.org/node/2817657 is committed.
+   */
+  protected function assertOrderInPage(array $items): void {
+    $session = $this->getSession();
+    $text = $session->getPage()->getHtml();
+    $strings = [];
+    foreach ($items as $item) {
+      if (($pos = strpos($text, $item)) === FALSE) {
+        throw new ExpectationException("Cannot find '$item' in the page", $session->getDriver());
+      }
+      $strings[$pos] = $item;
+    }
+    ksort($strings);
+    $ordered = implode(', ', array_map(function ($item) {
+      return "'$item'";
+    }, $items));
+    $this->assertSame($items, array_values($strings), "Found strings, ordered as: $ordered.");
+  }
+
+  /**
+   * Tests book outline AJAX request.
+   */
+  public function testBookAddOutline(): void {
+    $this->drupalLogin($this->drupalCreateUser(['create book content', 'create new books', 'add content to books']));
+    $this->drupalGet('node/add/book');
+    $assert_session = $this->assertSession();
+    $session = $this->getSession();
+    $page = $session->getPage();
+
+    $page->find('css', '#edit-book')->click();
+    $book_select = $page->findField("book[bid]");
+    $book_select->setValue('new');
+    $assert_session->waitForText('This will be the top-level page in this book.');
+    $assert_session->pageTextContains('This will be the top-level page in this book.');
+    $assert_session->pageTextNotContains('No book selected.');
+    $book_select->setValue(0);
+    $assert_session->waitForText('No book selected.');
+    $assert_session->pageTextContains('No book selected.');
+    $assert_session->pageTextNotContains('This will be the top-level page in this book.');
+  }
+
+}

core/modules/book/tests/src/Kernel/Block/BlockConfigSchemaTest.php

@@ -0,0 +1,77 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Kernel\Block;
+
+use Drupal\block\Entity\Block;
+use Drupal\Tests\SchemaCheckTestTrait;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests the block config schema.
+ *
+ * @group book
+ */
+class BlockConfigSchemaTest extends KernelTestBase {
+
+  use SchemaCheckTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'block',
+    'book',
+    'node',
+    // \Drupal\block\Entity\Block->preSave() calls system_region_list().
+    'system',
+    'user',
+  ];
+
+  /**
+   * The typed config manager.
+   *
+   * @var \Drupal\Core\Config\TypedConfigManagerInterface
+   */
+  protected $typedConfig;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->typedConfig = \Drupal::service('config.typed');
+    $this->installEntitySchema('node');
+    $this->installSchema('book', ['book']);
+    $this->container->get('theme_installer')->install(['stark']);
+  }
+
+  /**
+   * Tests the block config schema for block plugins.
+   */
+  public function testBlockConfigSchema(): void {
+    $id = strtolower($this->randomMachineName());
+    $block = Block::create([
+      'id' => $id,
+      'theme' => 'stark',
+      'weight' => 00,
+      'status' => TRUE,
+      'region' => 'content',
+      'plugin' => 'book_navigation',
+      'settings' => [
+        'label' => $this->randomMachineName(),
+        'provider' => 'system',
+        'label_display' => FALSE,
+      ],
+      'visibility' => [],
+    ]);
+    $block->save();
+
+    $config = $this->config("block.block.$id");
+    $this->assertEquals($id, $config->get('id'));
+    $this->assertConfigSchema($this->typedConfig, $config->getName(), $config->get());
+  }
+
+}

core/modules/book/tests/src/Kernel/BookInstallTest.php

@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Kernel;
+
+use Drupal\KernelTests\KernelTestBase;
+use Drupal\node\Entity\NodeType;
+
+/**
+ * Test installation of Book module.
+ *
+ * @group book
+ * @group legacy
+ */
+class BookInstallTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'node',
+    'system',
+  ];
+
+  /**
+   * Tests Book install with pre-existing content type.
+   *
+   * Tests that Book module can be installed if content type with machine name
+   * 'book' already exists.
+   */
+  public function testBookInstallWithPreexistingContentType(): void {
+    // Create a 'book' content type.
+    NodeType::create([
+      'type' => 'book',
+      'name' => 'Book',
+    ])->save();
+    // Install the Book module. Using the module installer service ensures that
+    // all the install rituals, including default and optional configuration
+    // import, are performed.
+    $status = $this->container->get('module_installer')->install(['book']);
+    $this->assertTrue($status, 'Book module installed successfully');
+  }
+
+}

core/modules/book/tests/src/Kernel/BookMultilingualTest.php

@@ -0,0 +1,346 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Kernel;
+
+use Drupal\Core\Language\LanguageInterface;
+use Drupal\Core\Link;
+use Drupal\Core\Routing\RouteMatch;
+use Drupal\Core\Url;
+use Drupal\KernelTests\KernelTestBase;
+use Drupal\language\Entity\ConfigurableLanguage;
+use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUrl;
+use Drupal\node\Entity\Node;
+use Drupal\node\Entity\NodeType;
+use Drupal\Tests\user\Traits\UserCreationTrait;
+use Drupal\user\Plugin\LanguageNegotiation\LanguageNegotiationUser;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Session\Session;
+use Symfony\Component\HttpFoundation\Session\Storage\MockArraySessionStorage;
+use Symfony\Component\Routing\Route;
+
+/**
+ * Tests multilingual books.
+ *
+ * @group book
+ * @group legacy
+ */
+class BookMultilingualTest extends KernelTestBase {
+
+  use UserCreationTrait;
+
+  /**
+   * The translation langcode.
+   */
+  const LANGCODE = 'de';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'system',
+    'user',
+    'node',
+    'field',
+    'text',
+    'book',
+    'language',
+    'content_translation',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    // Create the translation language.
+    $this->installConfig(['language']);
+    ConfigurableLanguage::createFromLangcode(self::LANGCODE)->save();
+    // Set up language negotiation.
+    $config = $this->config('language.types');
+    $config->set('configurable', [
+      LanguageInterface::TYPE_INTERFACE,
+      LanguageInterface::TYPE_CONTENT,
+    ]);
+    // The language being tested should only be available as the content
+    // language so subsequent tests catch errors where the interface language
+    // is used instead of the content language. For this, the interface
+    // language is set to the user language and ::setCurrentLanguage() will
+    // set the user language to the language not being tested.
+    $config->set('negotiation', [
+      LanguageInterface::TYPE_INTERFACE => [
+        'enabled' => [LanguageNegotiationUser::METHOD_ID => 0],
+      ],
+      LanguageInterface::TYPE_CONTENT => [
+        'enabled' => [LanguageNegotiationUrl::METHOD_ID => 0],
+      ],
+    ]);
+    $config->save();
+    $config = $this->config('language.negotiation');
+    $config->set('url.source', LanguageNegotiationUrl::CONFIG_DOMAIN);
+    $config->set('url.domains', [
+      'en' => 'en.book.test.domain',
+      self::LANGCODE => self::LANGCODE . '.book.test.domain',
+    ]);
+    $config->save();
+    $this->container->get('kernel')->rebuildContainer();
+
+    $this->installEntitySchema('node');
+    $this->installEntitySchema('user');
+    $this->installSchema('book', ['book']);
+    $this->installSchema('node', ['node_access']);
+    $this->installConfig(['node', 'book', 'field']);
+    $node_type = NodeType::create([
+      'type' => $this->randomMachineName(),
+      'name' => $this->randomString(),
+    ]);
+    $node_type->save();
+    $this->container->get('content_translation.manager')->setEnabled('node', $node_type->id(), TRUE);
+    $book_config = $this->config('book.settings');
+    $allowed_types = $book_config->get('allowed_types');
+    $allowed_types[] = $node_type->id();
+    $book_config->set('allowed_types', $allowed_types)->save();
+    // To test every possible combination of root-child / child-child, two
+    // trees are needed. The first level below the root needs to have two
+    // leaves and similarly a second level is needed with two-two leaves each:
+    //
+    //        1
+    //      /   \
+    //     /     \
+    //    2       3
+    //   / \     / \
+    //  /   \   /   \
+    // 4     5 6     7
+    //
+    // These are the actual node IDs, these are enforced as auto increment is
+    // not reliable.
+    //
+    // Similarly, the second tree root is node 8, the first two leaves are
+    // 9 and 10, the third level is 11, 12, 13, 14.
+    for ($root = 1; $root <= 8; $root += 7) {
+      for ($i = 0; $i <= 6; $i++) {
+        /** @var \Drupal\node\NodeInterface $node */
+        $node = Node::create([
+          'title' => $this->randomString(),
+          'type' => $node_type->id(),
+        ]);
+        $node->addTranslation(self::LANGCODE, [
+          'title' => $this->randomString(),
+        ]);
+        switch ($i) {
+          case 0:
+            $node->book['bid'] = 'new';
+            $node->book['pid'] = 0;
+            $node->book['depth'] = 1;
+            break;
+
+          case 1:
+          case 2:
+            $node->book['bid'] = $root;
+            $node->book['pid'] = $root;
+            $node->book['depth'] = 2;
+            break;
+
+          case 3:
+          case 4:
+            $node->book['bid'] = $root;
+            $node->book['pid'] = $root + 1;
+            $node->book['depth'] = 3;
+            break;
+
+          case 5:
+          case 6:
+            $node->book['bid'] = $root;
+            $node->book['pid'] = $root + 2;
+            $node->book['depth'] = 3;
+            break;
+        }
+        // This is necessary to make the table of contents consistent across
+        // test runs.
+        $node->book['weight'] = $i;
+        $node->nid->value = $root + $i;
+        $node->enforceIsNew();
+        $node->save();
+      }
+    }
+    \Drupal::currentUser()->setAccount($this->createUser(['access content']));
+  }
+
+  /**
+   * Tests various book manager methods return correct translations.
+   *
+   * @dataProvider langcodesProvider
+   */
+  public function testMultilingualBookManager(string $langcode): void {
+    $this->setCurrentLanguage($langcode);
+    /** @var \Drupal\book\BookManagerInterface $bm */
+    $bm = $this->container->get('book.manager');
+    $books = $bm->getAllBooks();
+    $this->assertNotEmpty($books);
+    foreach ($books as $book) {
+      $bid = (int) $book['bid'];
+      $build = $bm->bookTreeOutput($bm->bookTreeAllData($bid));
+      $items = $build['#items'];
+      $this->assertBookItemIsCorrectlyTranslated($items[$bid], $langcode);
+      $this->assertBookItemIsCorrectlyTranslated($items[$bid]['below'][$bid + 1], $langcode);
+      $this->assertBookItemIsCorrectlyTranslated($items[$bid]['below'][$bid + 1]['below'][$bid + 3], $langcode);
+      $this->assertBookItemIsCorrectlyTranslated($items[$bid]['below'][$bid + 1]['below'][$bid + 4], $langcode);
+      $this->assertBookItemIsCorrectlyTranslated($items[$bid]['below'][$bid + 2], $langcode);
+      $this->assertBookItemIsCorrectlyTranslated($items[$bid]['below'][$bid + 2]['below'][$bid + 5], $langcode);
+      $this->assertBookItemIsCorrectlyTranslated($items[$bid]['below'][$bid + 2]['below'][$bid + 6], $langcode);
+      $toc = $bm->getTableOfContents($bid, 4);
+      // Root entry does not have an indent.
+      $this->assertToCEntryIsCorrectlyTranslated($toc, $langcode, $bid, '');
+      // The direct children of the root have one indent.
+      $this->assertToCEntryIsCorrectlyTranslated($toc, $langcode, $bid + 1, '--');
+      $this->assertToCEntryIsCorrectlyTranslated($toc, $langcode, $bid + 2, '--');
+      // Their children have two indents.
+      $this->assertToCEntryIsCorrectlyTranslated($toc, $langcode, $bid + 3, '----');
+      $this->assertToCEntryIsCorrectlyTranslated($toc, $langcode, $bid + 4, '----');
+      $this->assertToCEntryIsCorrectlyTranslated($toc, $langcode, $bid + 5, '----');
+      $this->assertToCEntryIsCorrectlyTranslated($toc, $langcode, $bid + 6, '----');
+      // $bid might be a string.
+      $this->assertSame([$bid + 0, $bid + 1, $bid + 3, $bid + 4, $bid + 2, $bid + 5, $bid + 6], array_keys($toc));
+    }
+  }
+
+  /**
+   * Tests various book breadcrumb builder methods return correct translations.
+   *
+   * @dataProvider langcodesProvider
+   */
+  public function testMultilingualBookBreadcrumbBuilder(string $langcode): void {
+    $this->setCurrentLanguage($langcode);
+    // Test a level 3 node.
+    $nid = 7;
+    /** @var \Drupal\node\NodeInterface $node */
+    $node = Node::load($nid);
+    $route = new Route('/node/{node}');
+    $route_match = new RouteMatch('entity.node.canonical', $route, ['node' => $node], ['node' => $nid]);
+    /** @var \Drupal\book\BookBreadcrumbBuilder $bbb */
+    $bbb = $this->container->get('book.breadcrumb');
+    $links = $bbb->build($route_match)->getLinks();
+    $link = array_shift($links);
+    $rendered_link = (string) Link::fromTextAndUrl($link->getText(), $link->getUrl())->toString();
+    $this->assertStringContainsString("http://$langcode.book.test.domain/", $rendered_link);
+    $link = array_shift($links);
+    $this->assertNodeLinkIsCorrectlyTranslated(1, $link->getText(), $link->getUrl(), $langcode);
+    $link = array_shift($links);
+    $this->assertNodeLinkIsCorrectlyTranslated(3, $link->getText(), $link->getUrl(), $langcode);
+    $this->assertEmpty($links);
+  }
+
+  /**
+   * Tests the book export returns correct translations.
+   *
+   * @dataProvider langcodesProvider
+   */
+  public function testMultilingualBookExport(string $langcode): void {
+    $this->setCurrentLanguage($langcode);
+    /** @var \Drupal\book\BookExport $be */
+    $be = $this->container->get('book.export');
+    /** @var \Drupal\book\BookManagerInterface $bm */
+    $bm = $this->container->get('book.manager');
+    $books = $bm->getAllBooks();
+    $this->assertNotEmpty($books);
+    foreach ($books as $book) {
+      $contents = $be->bookExportHtml(Node::load($book['bid']))['#contents'][0];
+      $this->assertSame($contents["#node"]->language()->getId(), $langcode);
+      $this->assertSame($contents["#children"][0]["#node"]->language()->getId(), $langcode);
+      $this->assertSame($contents["#children"][1]["#node"]->language()->getId(), $langcode);
+      $this->assertSame($contents["#children"][0]["#children"][0]["#node"]->language()->getId(), $langcode);
+      $this->assertSame($contents["#children"][0]["#children"][1]["#node"]->language()->getId(), $langcode);
+      $this->assertSame($contents["#children"][1]["#children"][0]["#node"]->language()->getId(), $langcode);
+      $this->assertSame($contents["#children"][1]["#children"][1]["#node"]->language()->getId(), $langcode);
+    }
+  }
+
+  /**
+   * Data provider for ::testMultilingualBooks().
+   */
+  public static function langcodesProvider() {
+    return [
+      [self::LANGCODE],
+      ['en'],
+    ];
+  }
+
+  /**
+   * Sets the current language.
+   *
+   * @param string $langcode
+   *   The langcode. The content language will be set to this using the
+   *   appropriate domain while the user language will be set to something
+   *   else so subsequent tests catch errors where the interface language
+   *   is used instead of the content language.
+   */
+  protected function setCurrentLanguage(string $langcode): void {
+    $request = Request::create("http://$langcode.book.test.domain/");
+    $request->setSession(new Session(new MockArraySessionStorage()));
+    \Drupal::requestStack()->push($request);
+    $language_manager = $this->container->get('language_manager');
+    $language_manager->reset();
+    $current_user = \Drupal::currentUser();
+    $languages = $language_manager->getLanguages();
+    unset($languages[$langcode]);
+    $current_user->getAccount()->set('preferred_langcode', reset($languages)->getId());
+    $this->assertNotSame($current_user->getPreferredLangcode(), $langcode);
+  }
+
+  /**
+   * Asserts a book item is correctly translated.
+   *
+   * @param array $item
+   *   A book tree item.
+   * @param string $langcode
+   *   The language code for the requested translation.
+   *
+   * @internal
+   */
+  protected function assertBookItemIsCorrectlyTranslated(array $item, string $langcode): void {
+    $this->assertNodeLinkIsCorrectlyTranslated((int) $item['original_link']['nid'], $item['title'], $item['url'], $langcode);
+  }
+
+  /**
+   * Asserts a node link is correctly translated.
+   *
+   * @param int $nid
+   *   The node id.
+   * @param string $title
+   *   The expected title.
+   * @param \Drupal\Core\Url $url
+   *   The URL being tested.
+   * @param string $langcode
+   *   The language code.
+   *
+   * @internal
+   */
+  protected function assertNodeLinkIsCorrectlyTranslated(int $nid, string $title, Url $url, string $langcode): void {
+    $node = Node::load($nid);
+    $this->assertSame($node->getTranslation($langcode)->label(), $title);
+    $rendered_link = (string) Link::fromTextAndUrl($title, $url)->toString();
+    $this->assertStringContainsString("http://$langcode.book.test.domain/node/$nid", $rendered_link);
+  }
+
+  /**
+   * Asserts one entry in the table of contents is correct.
+   *
+   * @param array $toc
+   *   The entire table of contents array.
+   * @param string $langcode
+   *   The language code for the requested translation.
+   * @param int $nid
+   *   The node ID.
+   * @param string $indent
+   *   The indentation before the actual table of contents label.
+   *
+   * @internal
+   */
+  protected function assertToCEntryIsCorrectlyTranslated(array $toc, string $langcode, int $nid, string $indent): void {
+    $node = Node::load($nid);
+    $node_label = $node->getTranslation($langcode)->label();
+    $this->assertSame($indent . ' ' . $node_label, $toc[$nid]);
+  }
+
+}

core/modules/book/tests/src/Kernel/BookPendingRevisionTest.php

@@ -0,0 +1,111 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Kernel;
+
+use Drupal\node\Entity\Node;
+use Drupal\node\Entity\NodeType;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests that the Book module handles pending revisions correctly.
+ *
+ * @group book
+ * @group legacy
+ */
+class BookPendingRevisionTest extends KernelTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = [
+    'system',
+    'user',
+    'field',
+    'filter',
+    'text',
+    'node',
+    'book',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->installEntitySchema('user');
+    $this->installEntitySchema('node');
+    $this->installSchema('book', ['book']);
+    $this->installSchema('node', ['node_access']);
+    $this->installConfig(['node', 'book', 'field']);
+  }
+
+  /**
+   * Tests pending revision handling for books.
+   */
+  public function testBookWithPendingRevisions(): void {
+    $content_type = NodeType::create([
+      'type' => $this->randomMachineName(),
+      'name' => $this->randomString(),
+    ]);
+    $content_type->save();
+    $book_config = $this->config('book.settings');
+    $allowed_types = $book_config->get('allowed_types');
+    $allowed_types[] = $content_type->id();
+    $book_config->set('allowed_types', $allowed_types)->save();
+
+    // Create two top-level books a child.
+    $book_1 = Node::create(['title' => $this->randomString(), 'type' => $content_type->id()]);
+    $book_1->book['bid'] = 'new';
+    $book_1->save();
+    $book_1_child = Node::create(['title' => $this->randomString(), 'type' => $content_type->id()]);
+    $book_1_child->book['bid'] = $book_1->id();
+    $book_1_child->book['pid'] = $book_1->id();
+    $book_1_child->save();
+
+    $book_2 = Node::create(['title' => $this->randomString(), 'type' => $content_type->id()]);
+    $book_2->book['bid'] = 'new';
+    $book_2->save();
+
+    $child = Node::create(['title' => $this->randomString(), 'type' => $content_type->id()]);
+    $child->book['bid'] = $book_1->id();
+    $child->book['pid'] = $book_1->id();
+    $child->save();
+
+    // Try to move the child to a different book while saving it as a pending
+    // revision.
+    /** @var \Drupal\book\BookManagerInterface $book_manager */
+    $book_manager = $this->container->get('book.manager');
+
+    // Check that the API doesn't allow us to change the book outline for
+    // pending revisions.
+    $child->book['bid'] = $book_2->id();
+    $child->setNewRevision(TRUE);
+    $child->isDefaultRevision(FALSE);
+
+    $this->assertFalse($book_manager->updateOutline($child), 'A pending revision can not change the book outline.');
+
+    // Check that the API doesn't allow us to change the book parent for
+    // pending revisions.
+    $child = \Drupal::entityTypeManager()->getStorage('node')->loadUnchanged($child->id());
+    $child->book['pid'] = $book_1_child->id();
+    $child->setNewRevision(TRUE);
+    $child->isDefaultRevision(FALSE);
+
+    $this->assertFalse($book_manager->updateOutline($child), 'A pending revision can not change the book outline.');
+
+    // Check that the API doesn't allow us to change the book weight for
+    // pending revisions.
+    $child = \Drupal::entityTypeManager()->getStorage('node')->loadUnchanged($child->id());
+    $child->book['weight'] = 2;
+    $child->setNewRevision(TRUE);
+    $child->isDefaultRevision(FALSE);
+
+    $this->assertFalse($book_manager->updateOutline($child), 'A pending revision can not change the book outline.');
+  }
+
+}

core/modules/book/tests/src/Kernel/BookSettingsFormTest.php

@@ -0,0 +1,59 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Kernel;
+
+use Drupal\book\Form\BookSettingsForm;
+use Drupal\Core\Form\FormState;
+use Drupal\KernelTests\KernelTestBase;
+use Drupal\Tests\node\Traits\ContentTypeCreationTrait;
+
+/**
+ * @covers \Drupal\book\Form\BookSettingsForm
+ * @group book
+ * @group legacy
+ */
+class BookSettingsFormTest extends KernelTestBase {
+
+  use ContentTypeCreationTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'book',
+    'field',
+    'node',
+    'system',
+    'text',
+    'user',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->installConfig(['book', 'node']);
+    $this->createContentType(['type' => 'chapter']);
+    $this->createContentType(['type' => 'page']);
+  }
+
+  /**
+   * Tests that submitted values are processed and saved correctly.
+   */
+  public function testConfigValuesSavedCorrectly(): void {
+    $form_state = new FormState();
+    $form_state->setValues([
+      'book_allowed_types' => ['page', 'chapter', ''],
+      'book_child_type' => 'page',
+    ]);
+    $this->container->get('form_builder')->submitForm(BookSettingsForm::class, $form_state);
+
+    $config = $this->config('book.settings');
+    $this->assertSame(['chapter', 'page'], $config->get('allowed_types'));
+    $this->assertSame('page', $config->get('child_type'));
+  }
+
+}

core/modules/book/tests/src/Kernel/BookUninstallTest.php

@@ -0,0 +1,105 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Kernel;
+
+use Drupal\node\Entity\Node;
+use Drupal\node\Entity\NodeType;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests that the Book module cannot be uninstalled if books exist.
+ *
+ * @group book
+ * @group legacy
+ */
+class BookUninstallTest extends KernelTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = [
+    'system',
+    'user',
+    'field',
+    'filter',
+    'text',
+    'node',
+    'book',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->installEntitySchema('user');
+    $this->installEntitySchema('node');
+    $this->installSchema('book', ['book']);
+    $this->installSchema('node', ['node_access']);
+    $this->installConfig(['node', 'book', 'field']);
+    // For uninstall to work.
+    $this->installSchema('user', ['users_data']);
+  }
+
+  /**
+   * Tests the book_system_info_alter() method.
+   */
+  public function testBookUninstall(): void {
+    // No nodes exist.
+    $validation_reasons = \Drupal::service('module_installer')->validateUninstall(['book']);
+    $this->assertEquals([], $validation_reasons, 'The book module is not required.');
+
+    $content_type = NodeType::create([
+      'type' => $this->randomMachineName(),
+      'name' => $this->randomString(),
+    ]);
+    $content_type->save();
+    $book_config = $this->config('book.settings');
+    $allowed_types = $book_config->get('allowed_types');
+    $allowed_types[] = $content_type->id();
+    $book_config->set('allowed_types', $allowed_types)->save();
+
+    $node = Node::create(['title' => $this->randomString(), 'type' => $content_type->id()]);
+    $node->book['bid'] = 'new';
+    $node->save();
+
+    // One node in a book but not of type book.
+    $validation_reasons = \Drupal::service('module_installer')->validateUninstall(['book']);
+    $this->assertEquals(['To uninstall Book, delete all content that is part of a book'], $validation_reasons['book']);
+
+    $book_node = Node::create(['title' => $this->randomString(), 'type' => 'book']);
+    $book_node->book['bid'] = FALSE;
+    $book_node->save();
+
+    // Two nodes, one in a book but not of type book and one book node (which is
+    // not in a book).
+    $validation_reasons = \Drupal::service('module_installer')->validateUninstall(['book']);
+    $this->assertEquals(['To uninstall Book, delete all content that is part of a book'], $validation_reasons['book']);
+
+    $node->delete();
+    // One node of type book but not actually part of a book.
+    $validation_reasons = \Drupal::service('module_installer')->validateUninstall(['book']);
+    $this->assertEquals(['To uninstall Book, delete all content that has the Book content type'], $validation_reasons['book']);
+
+    $book_node->delete();
+    // No nodes exist therefore the book module is not required.
+    $module_data = \Drupal::service('extension.list.module')->getList();
+    $this->assertFalse(isset($module_data['book']->info['required']), 'The book module is not required.');
+
+    $node = Node::create(['title' => $this->randomString(), 'type' => $content_type->id()]);
+    $node->save();
+    // One node exists but is not part of a book therefore the book module is
+    // not required.
+    $validation_reasons = \Drupal::service('module_installer')->validateUninstall(['book']);
+    $this->assertEquals([], $validation_reasons, 'The book module is not required.');
+
+    // Uninstall the Book module and check the node type is deleted.
+    \Drupal::service('module_installer')->uninstall(['book']);
+    $this->assertNull(NodeType::load('book'), "The book node type does not exist.");
+  }
+
+}

core/modules/book/tests/src/Kernel/Migrate/d6/MigrateBookConfigsTest.php

@@ -0,0 +1,63 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Kernel\Migrate\d6;
+
+use Drupal\Tests\SchemaCheckTestTrait;
+use Drupal\Tests\migrate_drupal\Kernel\d6\MigrateDrupal6TestBase;
+
+/**
+ * Upgrade variables to book.settings.yml.
+ *
+ * @group book
+ * @group legacy
+ */
+class MigrateBookConfigsTest extends MigrateDrupal6TestBase {
+
+  use SchemaCheckTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['book'];
+
+  /**
+   * Gets the path to the fixture file.
+   */
+  protected function getFixtureFilePath() {
+    return __DIR__ . '/../../../../fixtures/drupal6.php';
+  }
+
+  /**
+   * Data provider for testBookSettings().
+   *
+   * @return array
+   *   The data for each test scenario.
+   */
+  public static function providerBookSettings() {
+    return [
+      // d6_book_settings was renamed to book_settings, but use the old alias to
+      // prove that it works.
+      // @see book_migration_plugins_alter()
+      ['d6_book_settings'],
+      ['book_settings'],
+    ];
+  }
+
+  /**
+   * Tests migration of book variables to book.settings.yml.
+   *
+   * @dataProvider providerBookSettings
+   */
+  public function testBookSettings($migration_id): void {
+    $this->executeMigration($migration_id);
+
+    $config = $this->config('book.settings');
+    $this->assertSame('book', $config->get('child_type'));
+    $this->assertSame('book pages', $config->get('block.navigation.mode'));
+    $this->assertSame(['book'], $config->get('allowed_types'));
+    $this->assertConfigSchema(\Drupal::service('config.typed'), 'book.settings', $config->get());
+  }
+
+}

core/modules/book/tests/src/Kernel/Migrate/d6/MigrateBookTest.php

@@ -0,0 +1,108 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Kernel\Migrate\d6;
+
+use Drupal\Tests\migrate_drupal\Kernel\d6\MigrateDrupal6TestBase;
+use Drupal\node\Entity\Node;
+
+/**
+ * Upgrade book structure.
+ *
+ * @group book
+ * @group legacy
+ */
+class MigrateBookTest extends MigrateDrupal6TestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['book', 'node'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->installSchema('book', ['book']);
+    $this->installSchema('node', ['node_access']);
+    $this->migrateUsers(FALSE);
+    $this->installConfig(['node']);
+    $this->executeMigrations([
+      'd6_node_settings',
+      'd6_node_type',
+      'd6_node',
+      'd6_book',
+    ]);
+  }
+
+  /**
+   * Gets the path to the fixture file.
+   */
+  protected function getFixtureFilePath() {
+    return __DIR__ . '/../../../../fixtures/drupal6.php';
+  }
+
+  /**
+   * Tests the Drupal 6 book structure to Drupal 8 migration.
+   */
+  public function testBook(): void {
+    $nodes = Node::loadMultiple([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+    $this->assertSame('1', $nodes[1]->book['bid']);
+    $this->assertSame('0', $nodes[1]->book['pid']);
+
+    $this->assertSame('1', $nodes[2]->book['bid']);
+    $this->assertSame('1', $nodes[2]->book['pid']);
+
+    $this->assertSame('1', $nodes[3]->book['bid']);
+    $this->assertSame('1', $nodes[3]->book['pid']);
+
+    $this->assertSame('1', $nodes[4]->book['bid']);
+    $this->assertSame('3', $nodes[4]->book['pid']);
+
+    $this->assertSame('1', $nodes[5]->book['bid']);
+    $this->assertSame('3', $nodes[5]->book['pid']);
+
+    $this->assertSame('6', $nodes[6]->book['bid']);
+    $this->assertSame('0', $nodes[6]->book['pid']);
+
+    $this->assertSame('6', $nodes[7]->book['bid']);
+    $this->assertSame('6', $nodes[7]->book['pid']);
+
+    $this->assertSame('6', $nodes[8]->book['bid']);
+    $this->assertSame('6', $nodes[8]->book['pid']);
+
+    $this->assertSame('6', $nodes[9]->book['bid']);
+    $this->assertSame('8', $nodes[9]->book['pid']);
+
+    $this->assertSame('6', $nodes[10]->book['bid']);
+    $this->assertSame('8', $nodes[10]->book['pid']);
+
+    $tree = \Drupal::service('book.manager')->bookTreeAllData(1);
+    $this->assertSame('1', $tree['50000 Birds 1']['link']['nid']);
+    $this->assertSame('2', $tree['50000 Birds 1']['below']['50000 Emu 2']['link']['nid']);
+    $this->assertSame([], $tree['50000 Birds 1']['below']['50000 Emu 2']['below']);
+    $this->assertSame('3', $tree['50000 Birds 1']['below']['50000 Parrots 3']['link']['nid']);
+    $this->assertSame('4', $tree['50000 Birds 1']['below']['50000 Parrots 3']['below']['50000 Kea 4']['link']['nid']);
+    $this->assertSame([], $tree['50000 Birds 1']['below']['50000 Parrots 3']['below']['50000 Kea 4']['below']);
+    $this->assertSame('5', $tree['50000 Birds 1']['below']['50000 Parrots 3']['below']['50000 Kakapo 5']['link']['nid']);
+    $this->assertSame([], $tree['50000 Birds 1']['below']['50000 Parrots 3']['below']['50000 Kakapo 5']['below']);
+
+    $tree = \Drupal::service('book.manager')->bookTreeAllData(6);
+    $this->assertSame('6', $tree['50000 Tree 6']['link']['nid']);
+    $this->assertSame('7', $tree['50000 Tree 6']['below']['50000 Rimu 7']['link']['nid']);
+    $this->assertSame([], $tree['50000 Tree 6']['below']['50000 Rimu 7']['below']);
+    $this->assertSame('8', $tree['50000 Tree 6']['below']['50000 Oaks 8']['link']['nid']);
+    $this->assertSame('9', $tree['50000 Tree 6']['below']['50000 Oaks 8']['below']['50000 Cork oak 9']['link']['nid']);
+    $this->assertSame([], $tree['50000 Tree 6']['below']['50000 Oaks 8']['below']['50000 Cork oak 9']['below']);
+    $this->assertSame('10', $tree['50000 Tree 6']['below']['50000 Oaks 8']['below']['50000 White oak 10']['link']['nid']);
+    $this->assertSame([], $tree['50000 Tree 6']['below']['50000 Oaks 8']['below']['50000 White oak 10']['below']);
+
+    // Set the d6_book migration to update and re run the migration.
+    $id_map = $this->migration->getIdMap();
+    $id_map->prepareUpdate();
+    $this->executeMigration('d6_book');
+  }
+
+}

core/modules/book/tests/src/Kernel/Migrate/d7/MigrateBookConfigsTest.php

@@ -0,0 +1,51 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Kernel\Migrate\d7;
+
+use Drupal\Tests\migrate_drupal\Kernel\d7\MigrateDrupal7TestBase;
+use Drupal\Tests\SchemaCheckTestTrait;
+
+/**
+ * Tests the migration of Book settings.
+ *
+ * @group book
+ * @group legacy
+ */
+class MigrateBookConfigsTest extends MigrateDrupal7TestBase {
+
+  use SchemaCheckTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['book', 'node'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->executeMigration('book_settings');
+  }
+
+  /**
+   * Gets the path to the fixture file.
+   */
+  protected function getFixtureFilePath() {
+    return __DIR__ . '/../../../../fixtures/drupal7.php';
+  }
+
+  /**
+   * Tests migration of book variables to book.settings.yml.
+   */
+  public function testBookSettings(): void {
+    $config = $this->config('book.settings');
+    $this->assertSame('book', $config->get('child_type'));
+    $this->assertSame('all pages', $config->get('block.navigation.mode'));
+    $this->assertSame(['book'], $config->get('allowed_types'));
+    $this->assertConfigSchema(\Drupal::service('config.typed'), 'book.settings', $config->get());
+  }
+
+}

core/modules/book/tests/src/Kernel/Migrate/d7/MigrateBookTest.php

@@ -0,0 +1,111 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Kernel\Migrate\d7;
+
+use Drupal\Tests\migrate_drupal\Kernel\d7\MigrateDrupal7TestBase;
+use Drupal\node\Entity\Node;
+
+/**
+ * Tests migration of book structures from Drupal 7.
+ *
+ * @group book
+ * @group legacy
+ */
+class MigrateBookTest extends MigrateDrupal7TestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'book',
+    'menu_ui',
+    'node',
+    'text',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->installSchema('book', ['book']);
+    $this->installSchema('node', ['node_access']);
+    $this->migrateUsers(FALSE);
+    $this->migrateContentTypes();
+    $this->executeMigrations([
+      'd7_node',
+      'd7_book',
+    ]);
+  }
+
+  /**
+   * Gets the path to the fixture file.
+   */
+  protected function getFixtureFilePath() {
+    return __DIR__ . '/../../../../fixtures/drupal7.php';
+  }
+
+  /**
+   * Tests the Drupal 7 book structure to Drupal 8 migration.
+   */
+  public function testBook(): void {
+    $nodes = Node::loadMultiple([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+    $this->assertSame('1', $nodes[1]->book['bid']);
+    $this->assertSame('0', $nodes[1]->book['pid']);
+
+    $this->assertSame('1', $nodes[2]->book['bid']);
+    $this->assertSame('1', $nodes[2]->book['pid']);
+
+    $this->assertSame('1', $nodes[3]->book['bid']);
+    $this->assertSame('1', $nodes[3]->book['pid']);
+
+    $this->assertSame('1', $nodes[4]->book['bid']);
+    $this->assertSame('3', $nodes[4]->book['pid']);
+
+    $this->assertSame('1', $nodes[5]->book['bid']);
+    $this->assertSame('3', $nodes[5]->book['pid']);
+
+    $this->assertSame('6', $nodes[6]->book['bid']);
+    $this->assertSame('0', $nodes[6]->book['pid']);
+
+    $this->assertSame('6', $nodes[7]->book['bid']);
+    $this->assertSame('6', $nodes[7]->book['pid']);
+
+    $this->assertSame('6', $nodes[8]->book['bid']);
+    $this->assertSame('6', $nodes[8]->book['pid']);
+
+    $this->assertSame('6', $nodes[9]->book['bid']);
+    $this->assertSame('8', $nodes[9]->book['pid']);
+
+    $this->assertSame('6', $nodes[10]->book['bid']);
+    $this->assertSame('8', $nodes[10]->book['pid']);
+
+    $tree = \Drupal::service('book.manager')->bookTreeAllData(1);
+    $this->assertSame('1', $tree['50000 Birds 1']['link']['nid']);
+    $this->assertSame('2', $tree['50000 Birds 1']['below']['50000 Emu 2']['link']['nid']);
+    $this->assertSame([], $tree['50000 Birds 1']['below']['50000 Emu 2']['below']);
+    $this->assertSame('3', $tree['50000 Birds 1']['below']['50000 Parrots 3']['link']['nid']);
+    $this->assertSame('4', $tree['50000 Birds 1']['below']['50000 Parrots 3']['below']['50000 Kea 4']['link']['nid']);
+    $this->assertSame([], $tree['50000 Birds 1']['below']['50000 Parrots 3']['below']['50000 Kea 4']['below']);
+    $this->assertSame('5', $tree['50000 Birds 1']['below']['50000 Parrots 3']['below']['50000 Kakapo 5']['link']['nid']);
+    $this->assertSame([], $tree['50000 Birds 1']['below']['50000 Parrots 3']['below']['50000 Kakapo 5']['below']);
+
+    $tree = \Drupal::service('book.manager')->bookTreeAllData(6);
+    $this->assertSame('6', $tree['50000 Tree 6']['link']['nid']);
+    $this->assertSame('7', $tree['50000 Tree 6']['below']['50000 Rimu 7']['link']['nid']);
+    $this->assertSame([], $tree['50000 Tree 6']['below']['50000 Rimu 7']['below']);
+    $this->assertSame('8', $tree['50000 Tree 6']['below']['50000 Oaks 8']['link']['nid']);
+    $this->assertSame('9', $tree['50000 Tree 6']['below']['50000 Oaks 8']['below']['50000 Cork oak 9']['link']['nid']);
+    $this->assertSame([], $tree['50000 Tree 6']['below']['50000 Oaks 8']['below']['50000 Cork oak 9']['below']);
+    $this->assertSame('10', $tree['50000 Tree 6']['below']['50000 Oaks 8']['below']['50000 White oak 10']['link']['nid']);
+    $this->assertSame([], $tree['50000 Tree 6']['below']['50000 Oaks 8']['below']['50000 White oak 10']['below']);
+
+    // Set the d7_book migration to update and re run the migration.
+    $id_map = $this->migration->getIdMap();
+    $id_map->prepareUpdate();
+    $this->executeMigration('d7_book');
+  }
+
+}

core/modules/book/tests/src/Kernel/Plugin/migrate/source/BookTest.php

@@ -0,0 +1,89 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Kernel\Plugin\migrate\source;
+
+use Drupal\Tests\migrate\Kernel\MigrateSqlSourceTestBase;
+
+// cspell:ignore mlid plid
+
+/**
+ * @covers \Drupal\book\Plugin\migrate\source\Book
+ * @group book
+ * @group legacy
+ */
+class BookTest extends MigrateSqlSourceTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['book', 'migrate_drupal', 'node'];
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function providerSource() {
+    $tests = [];
+
+    // The source data.
+    $tests[0]['source_data']['book'] = [
+      [
+        'mlid' => '1',
+        'nid' => '4',
+        'bid' => '4',
+      ],
+    ];
+    $tests[0]['source_data']['menu_links'] = [
+      [
+        'menu_name' => 'book-toc-1',
+        'mlid' => '1',
+        'plid' => '0',
+        'link_path' => 'node/4',
+        'router_path' => 'node/%',
+        'link_title' => 'Test top book title',
+        'options' => 'a:0:{}',
+        'module' => 'book',
+        'hidden' => '0',
+        'external' => '0',
+        'has_children' => '1',
+        'expanded' => '0',
+        'weight' => '-10',
+        'depth' => '1',
+        'customized' => '0',
+        'p1' => '1',
+        'p2' => '0',
+        'p3' => '0',
+        'p4' => '0',
+        'p5' => '0',
+        'p6' => '0',
+        'p7' => '0',
+        'p8' => '0',
+        'p9' => '0',
+        'updated' => '0',
+      ],
+    ];
+
+    // The expected results.
+    $tests[0]['expected_data'] = [
+      [
+        'nid' => '4',
+        'bid' => '4',
+        'mlid' => '1',
+        'plid' => '0',
+        'weight' => '-10',
+        'p1' => '1',
+        'p2' => '0',
+        'p3' => '0',
+        'p4' => '0',
+        'p5' => '0',
+        'p6' => '0',
+        'p7' => '0',
+        'p8' => '0',
+        'p9' => '0',
+      ],
+    ];
+    return $tests;
+  }
+
+}

core/modules/book/tests/src/Unit/BookManagerTest.php

@@ -0,0 +1,142 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Unit;
+
+use Drupal\book\BookManager;
+use Drupal\Core\Cache\CacheBackendInterface;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @coversDefaultClass \Drupal\book\BookManager
+ * @group book
+ * @group legacy
+ */
+class BookManagerTest extends UnitTestCase {
+
+  /**
+   * The mocked entity type manager.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeManager|\PHPUnit\Framework\MockObject\MockObject
+   */
+  protected $entityTypeManager;
+
+  /**
+   * The mocked language manager.
+   *
+   * @var \Drupal\Core\Language\LanguageManager|\PHPUnit\Framework\MockObject\MockObject
+   */
+  protected $languageManager;
+
+  /**
+   * The mocked entity repository.
+   *
+   * @var \Drupal\Core\Entity\EntityRepositoryInterface|\PHPUnit\Framework\MockObject\MockObject
+   */
+  protected $entityRepository;
+
+  /**
+   * The mocked config factory.
+   *
+   * @var \Drupal\Core\Config\ConfigFactory|\PHPUnit\Framework\MockObject\MockObject
+   */
+  protected $configFactory;
+
+  /**
+   * The mocked translation manager.
+   *
+   * @var \Drupal\Core\StringTranslation\TranslationInterface|\PHPUnit\Framework\MockObject\MockObject
+   */
+  protected $translation;
+
+  /**
+   * The mocked renderer.
+   *
+   * @var \Drupal\Core\Render\RendererInterface|\PHPUnit\Framework\MockObject\MockObject
+   */
+  protected $renderer;
+
+  /**
+   * The tested book manager.
+   *
+   * @var \Drupal\book\BookManager
+   */
+  protected $bookManager;
+
+  /**
+   * Book outline storage.
+   *
+   * @var \Drupal\book\BookOutlineStorageInterface
+   */
+  protected $bookOutlineStorage;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->entityTypeManager = $this->createMock(EntityTypeManagerInterface::class);
+    $this->translation = $this->getStringTranslationStub();
+    $this->configFactory = $this->getConfigFactoryStub([]);
+    $this->bookOutlineStorage = $this->createMock('Drupal\book\BookOutlineStorageInterface');
+    $this->renderer = $this->createMock('\Drupal\Core\Render\RendererInterface');
+    $this->languageManager = $this->createMock('Drupal\Core\Language\LanguageManagerInterface');
+    $this->entityRepository = $this->createMock('Drupal\Core\Entity\EntityRepositoryInterface');
+    // Used for both book manager cache services: backend chain and memory.
+    $cache = $this->createMock(CacheBackendInterface::class);
+    $this->bookManager = new BookManager($this->entityTypeManager, $this->translation, $this->configFactory, $this->bookOutlineStorage, $this->renderer, $this->languageManager, $this->entityRepository, $cache, $cache);
+  }
+
+  /**
+   * Tests the getBookParents() method.
+   *
+   * @dataProvider providerTestGetBookParents
+   */
+  public function testGetBookParents($book, $parent, $expected): void {
+    $this->assertEquals($expected, $this->bookManager->getBookParents($book, $parent));
+  }
+
+  /**
+   * Provides test data for testGetBookParents.
+   *
+   * @return array
+   *   The test data.
+   */
+  public static function providerTestGetBookParents() {
+    $empty = [
+      'p1' => 0,
+      'p2' => 0,
+      'p3' => 0,
+      'p4' => 0,
+      'p5' => 0,
+      'p6' => 0,
+      'p7' => 0,
+      'p8' => 0,
+      'p9' => 0,
+    ];
+    return [
+      // Provides a book without an existing parent.
+      [
+        ['pid' => 0, 'nid' => 12],
+        [],
+        ['depth' => 1, 'p1' => 12] + $empty,
+      ],
+      // Provides a book with an existing parent.
+      [
+        ['pid' => 11, 'nid' => 12],
+        ['nid' => 11, 'depth' => 1, 'p1' => 11],
+        ['depth' => 2, 'p1' => 11, 'p2' => 12] + $empty,
+      ],
+      // Provides a book with two existing parents.
+      [
+        ['pid' => 11, 'nid' => 12],
+        ['nid' => 11, 'depth' => 2, 'p1' => 10, 'p2' => 11],
+        ['depth' => 3, 'p1' => 10, 'p2' => 11, 'p3' => 12] + $empty,
+      ],
+    ];
+  }
+
+}

core/modules/book/tests/src/Unit/BookUninstallValidatorTest.php

@@ -0,0 +1,98 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Unit;
+
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @coversDefaultClass \Drupal\book\BookUninstallValidator
+ * @group book
+ * @group legacy
+ */
+class BookUninstallValidatorTest extends UnitTestCase {
+
+  /**
+   * @var \Drupal\book\BookUninstallValidator|\PHPUnit\Framework\MockObject\MockObject
+   */
+  protected $bookUninstallValidator;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->bookUninstallValidator = $this->getMockBuilder('Drupal\book\BookUninstallValidator')
+      ->disableOriginalConstructor()
+      ->onlyMethods(['hasBookOutlines', 'hasBookNodes'])
+      ->getMock();
+    $this->bookUninstallValidator->setStringTranslation($this->getStringTranslationStub());
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateNotBook(): void {
+    $this->bookUninstallValidator->expects($this->never())
+      ->method('hasBookOutlines');
+    $this->bookUninstallValidator->expects($this->never())
+      ->method('hasBookNodes');
+
+    $module = 'not_book';
+    $expected = [];
+    $reasons = $this->bookUninstallValidator->validate($module);
+    $this->assertEquals($expected, $reasons);
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateEntityQueryWithoutResults(): void {
+    $this->bookUninstallValidator->expects($this->once())
+      ->method('hasBookOutlines')
+      ->willReturn(FALSE);
+    $this->bookUninstallValidator->expects($this->once())
+      ->method('hasBookNodes')
+      ->willReturn(FALSE);
+
+    $module = 'book';
+    $expected = [];
+    $reasons = $this->bookUninstallValidator->validate($module);
+    $this->assertEquals($expected, $reasons);
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateEntityQueryWithResults(): void {
+    $this->bookUninstallValidator->expects($this->once())
+      ->method('hasBookOutlines')
+      ->willReturn(FALSE);
+    $this->bookUninstallValidator->expects($this->once())
+      ->method('hasBookNodes')
+      ->willReturn(TRUE);
+
+    $module = 'book';
+    $expected = ['To uninstall Book, delete all content that has the Book content type'];
+    $reasons = $this->bookUninstallValidator->validate($module);
+    $this->assertEquals($expected, $reasons);
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateOutlineStorage(): void {
+    $this->bookUninstallValidator->expects($this->once())
+      ->method('hasBookOutlines')
+      ->willReturn(TRUE);
+    $this->bookUninstallValidator->expects($this->never())
+      ->method('hasBookNodes');
+
+    $module = 'book';
+    $expected = ['To uninstall Book, delete all content that is part of a book'];
+    $reasons = $this->bookUninstallValidator->validate($module);
+    $this->assertEquals($expected, $reasons);
+  }
+
+}

core/modules/book/tests/src/Unit/Menu/BookLocalTasksTest.php

@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\book\Unit\Menu;
+
+use Drupal\Tests\Core\Menu\LocalTaskIntegrationTestBase;
+
+/**
+ * Tests existence of book local tasks.
+ *
+ * @group book
+ * @group legacy
+ */
+class BookLocalTasksTest extends LocalTaskIntegrationTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    $this->directoryList = [
+      'book' => 'core/modules/book',
+      'node' => 'core/modules/node',
+    ];
+    parent::setUp();
+  }
+
+  /**
+   * Tests local task existence.
+   *
+   * @dataProvider getBookAdminRoutes
+   */
+  public function testBookAdminLocalTasks($route): void {
+
+    $this->assertLocalTasks($route, [
+      0 => ['book.admin', 'book.settings'],
+    ]);
+  }
+
+  /**
+   * Provides a list of routes to test.
+   */
+  public static function getBookAdminRoutes() {
+    return [
+      ['book.admin'],
+      ['book.settings'],
+    ];
+  }
+
+  /**
+   * Tests local task existence.
+   *
+   * @dataProvider getBookNodeRoutes
+   */
+  public function testBookNodeLocalTasks($route): void {
+    $this->assertLocalTasks($route, [
+      0 => ['entity.node.book_outline_form', 'entity.node.canonical', 'entity.node.edit_form', 'entity.node.delete_form', 'entity.node.version_history'],
+    ]);
+  }
+
+  /**
+   * Provides a list of routes to test.
+   */
+  public static function getBookNodeRoutes() {
+    return [
+      ['entity.node.canonical'],
+      ['entity.node.book_outline_form'],
+    ];
+  }
+
+}