class ForumTest

class ForumTest extends BrowserTestBase {
    
    /**
     * Modules to enable.
     *
     * @var array
     */
    protected static $modules = [
        'taxonomy',
        'comment',
        'forum',
        'node',
        'block',
        'menu_ui',
        'help',
    ];
    
    /**
     * {@inheritdoc}
     */
    protected $defaultTheme = 'starterkit_theme';
    
    /**
     * A user with various administrative privileges.
     */
    protected $adminUser;
    
    /**
     * A user that can create forum topics and edit its own topics.
     */
    protected $editOwnTopicsUser;
    
    /**
     * A user that can create, edit, and delete forum topics.
     */
    protected $editAnyTopicsUser;
    
    /**
     * A user with no special privileges.
     */
    protected $webUser;
    
    /**
     * An administrative user who can bypass comment approval.
     */
    protected $postCommentUser;
    
    /**
     * An array representing a forum container.
     */
    protected $forumContainer;
    
    /**
     * An array representing a forum.
     */
    protected $forum;
    
    /**
     * An array representing a root forum.
     */
    protected $rootForum;
    
    /**
     * An array of forum topic node IDs.
     */
    protected $nids;
    
    /**
     * {@inheritdoc}
     */
    protected function setUp() : void {
        parent::setUp();
        $this->drupalPlaceBlock('system_breadcrumb_block');
        $this->drupalPlaceBlock('page_title_block');
        // Create users.
        $this->adminUser = $this->drupalCreateUser([
            'access administration pages',
            'access help pages',
            'administer modules',
            'administer blocks',
            'administer forums',
            'administer menu',
            'administer taxonomy',
            'create forum content',
            'access comments',
        ]);
        $this->editAnyTopicsUser = $this->drupalCreateUser([
            'access administration pages',
            'access help pages',
            'create forum content',
            'edit any forum content',
            'delete any forum content',
        ]);
        $this->editOwnTopicsUser = $this->drupalCreateUser([
            'create forum content',
            'edit own forum content',
            'delete own forum content',
        ]);
        $this->webUser = $this->drupalCreateUser();
        $this->postCommentUser = $this->drupalCreateUser([
            'administer content types',
            'create forum content',
            'post comments',
            'skip comment approval',
            'access comments',
        ]);
        $this->drupalPlaceBlock('help_block', [
            'region' => 'help',
        ]);
        $this->drupalPlaceBlock('local_actions_block');
    }
    
    /**
     * Tests forum functionality through the admin and user interfaces.
     */
    public function testForum() : void {
        // Check that the basic forum install creates a default forum topic
        $this->drupalGet('/forum');
        // Look for the "General discussion" default forum
        $this->assertSession()
            ->linkExists('General discussion');
        $this->assertSession()
            ->linkByHrefExists('/forum/1');
        // Check the presence of expected cache tags.
        $this->assertSession()
            ->responseHeaderContains('X-Drupal-Cache-Tags', 'config:forum.settings');
        $this->drupalGet(Url::fromRoute('forum.page', [
            'taxonomy_term' => 1,
        ]));
        $this->assertSession()
            ->responseHeaderContains('X-Drupal-Cache-Tags', 'config:forum.settings');
        // Do the admin tests.
        $this->doAdminTests($this->adminUser);
        // Check display order.
        $display = EntityViewDisplay::load('node.forum.default');
        $body = $display->getComponent('body');
        $comment = $display->getComponent('comment_forum');
        $taxonomy = $display->getComponent('taxonomy_forums');
        // Assert field order is body » taxonomy » comments.
        $this->assertLessThan($body['weight'], $taxonomy['weight']);
        $this->assertLessThan($comment['weight'], $body['weight']);
        // Check form order.
        $display = EntityFormDisplay::load('node.forum.default');
        $body = $display->getComponent('body');
        $comment = $display->getComponent('comment_forum');
        $taxonomy = $display->getComponent('taxonomy_forums');
        // Assert category comes before body in order.
        $this->assertLessThan($body['weight'], $taxonomy['weight']);
        $this->generateForumTopics();
        // Log in an unprivileged user to view the forum topics and generate an
        // active forum topics list.
        $this->drupalLogin($this->webUser);
        // Verify that this user is shown a message that they may not post content.
        $this->drupalGet('forum/' . $this->forum['tid']);
        $this->assertSession()
            ->pageTextContains('You are not allowed to post new content in the forum');
        // Log in, and do basic tests for a user with permission to edit any forum
        // content.
        $this->doBasicTests($this->editAnyTopicsUser, TRUE);
        // Create a forum node authored by this user.
        $any_topics_user_node = $this->createForumTopic($this->forum, FALSE);
        // Log in, and do basic tests for a user with permission to edit only its
        // own forum content.
        $this->doBasicTests($this->editOwnTopicsUser, FALSE);
        // Create a forum node authored by this user.
        $own_topics_user_node = $this->createForumTopic($this->forum, FALSE);
        // Verify that this user cannot edit forum content authored by another user.
        $this->verifyForums($any_topics_user_node, FALSE, 403);
        // Verify that this user is shown a local task to add new forum content.
        $this->drupalGet('forum');
        $this->assertSession()
            ->linkExists('Add new Forum topic');
        $this->drupalGet('forum/' . $this->forum['tid']);
        $this->assertSession()
            ->linkExists('Add new Forum topic');
        // Log in a user with permission to edit any forum content.
        $this->drupalLogin($this->editAnyTopicsUser);
        // Verify that this user can edit forum content authored by another user.
        $this->verifyForums($own_topics_user_node, TRUE);
        // Verify the topic and post counts on the forum page.
        $this->drupalGet('forum');
        // Find the table row for the forum that has new posts. This cannot be
        // reliably identified by any CSS selector or its position in the table,
        // so look for an element with the "New posts" title and traverse up the
        // document tree until we get to the table row that contains it.
        $row = $this->assertSession()
            ->elementExists('css', '[title="New posts"]');
        while ($row && $row->getTagName() !== 'tr') {
            $row = $row->getParent();
        }
        $this->assertNotEmpty($row);
        $cells = $row->findAll('css', 'td');
        $this->assertCount(4, $cells);
        // Topics cell contains number of topics (6), number of unread topics (also
        // 6), and the forum name.
        $this->assertEquals('6 6 new posts in forum ' . $this->forum['name'], $cells[1]->getText(), 'Number of topics found.');
        // Verify total number of posts in forum.
        $this->assertEquals('6', $cells[2]->getText(), 'Number of posts found.');
        // Test loading multiple forum nodes on the front page.
        $this->drupalLogin($this->drupalCreateUser([
            'administer content types',
            'create forum content',
            'post comments',
        ]));
        $this->drupalGet('admin/structure/types/manage/forum');
        $this->submitForm([
            'options[promote]' => 'promote',
        ], 'Save');
        $this->createForumTopic($this->forum, FALSE);
        $this->createForumTopic($this->forum, FALSE);
        $this->drupalGet('node');
        // Test adding a comment to a forum topic.
        $node = $this->createForumTopic($this->forum, FALSE);
        $edit = [];
        $edit['comment_body[0][value]'] = $this->randomMachineName();
        $this->drupalGet('node/' . $node->id());
        $this->submitForm($edit, 'Save');
        $this->assertSession()
            ->statusCodeEquals(200);
        // Test editing a forum topic that has a comment.
        $this->drupalLogin($this->editAnyTopicsUser);
        $this->drupalGet('forum/' . $this->forum['tid']);
        $this->drupalGet('node/' . $node->id() . '/edit');
        $this->submitForm([], 'Save');
        $this->assertSession()
            ->statusCodeEquals(200);
        // Test the root forum page title change.
        $this->drupalGet('forum');
        $this->assertSession()
            ->responseHeaderContains('X-Drupal-Cache-Tags', 'config:taxonomy.vocabulary.' . $this->forum['vid']);
        $this->assertSession()
            ->titleEquals('Forums | Drupal');
        $vocabulary = Vocabulary::load($this->forum['vid']);
        $vocabulary->set('name', 'Discussions');
        $vocabulary->save();
        $this->drupalGet('forum');
        $this->assertSession()
            ->titleEquals('Discussions | Drupal');
        // Test anonymous action link.
        $this->drupalLogout();
        $this->drupalGet('forum/' . $this->forum['tid']);
        $this->assertSession()
            ->linkExists('Log in to post new content in the forum.');
    }
    
    /**
     * Tests that forum nodes can't be added without a parent.
     *
     * Verifies that forum nodes are not created without choosing "forum" from the
     * select list.
     */
    public function testAddOrphanTopic() : void {
        // Must remove forum topics to test creating orphan topics.
        $vid = $this->config('forum.settings')
            ->get('vocabulary');
        $tids = \Drupal::entityQuery('taxonomy_term')->accessCheck(FALSE)
            ->condition('vid', $vid)
            ->execute();
        $term_storage = \Drupal::entityTypeManager()->getStorage('taxonomy_term');
        $terms = $term_storage->loadMultiple($tids);
        $term_storage->delete($terms);
        // Create an orphan forum item.
        $edit = [];
        $edit['title[0][value]'] = $this->randomMachineName(10);
        $edit['body[0][value]'] = $this->randomMachineName(120);
        $this->drupalLogin($this->adminUser);
        $this->drupalGet('node/add/forum');
        $this->submitForm($edit, 'Save');
        $nid_count = $this->container
            ->get('entity_type.manager')
            ->getStorage('node')
            ->getQuery()
            ->accessCheck(FALSE)
            ->count()
            ->execute();
        $this->assertEquals(0, $nid_count, 'A forum node was not created when missing a forum vocabulary.');
        // Reset the defaults for future tests.
        \Drupal::service('module_installer')->install([
            'forum',
        ]);
    }
    
    /**
     * Runs admin tests on the admin user.
     *
     * @param object $user
     *   The logged-in user.
     */
    private function doAdminTests($user) {
        // Log in the user.
        $this->drupalLogin($user);
        // Add forum to the Tools menu.
        $edit = [];
        $this->drupalGet('admin/structure/menu/manage/tools');
        $this->submitForm($edit, 'Save');
        $this->assertSession()
            ->statusCodeEquals(200);
        // Edit forum taxonomy.
        // Restoration of the settings fails and causes subsequent tests to fail.
        $this->editForumVocabulary();
        // Create forum container.
        $this->forumContainer = $this->createForum('container');
        // Verify "edit container" link exists and functions correctly.
        $this->drupalGet('admin/structure/forum');
        // Verify help text is shown.
        $this->assertSession()
            ->pageTextContains('Forums contain forum topics. Use containers to group related forums');
        // Verify action links are there.
        $this->assertSession()
            ->linkExists('Add forum');
        $this->assertSession()
            ->linkExists('Add container');
        $this->clickLink('edit container');
        $this->assertSession()
            ->pageTextContains('Edit container');
        // Create forum inside the forum container.
        $this->forum = $this->createForum('forum', $this->forumContainer['tid']);
        // Verify the "edit forum" link exists and functions correctly.
        $this->drupalGet('admin/structure/forum');
        $this->clickLink('edit forum');
        $this->assertSession()
            ->pageTextContains('Edit forum');
        // Navigate back to forum structure page.
        $this->drupalGet('admin/structure/forum');
        // Create second forum in container, destined to be deleted below.
        $delete_forum = $this->createForum('forum', $this->forumContainer['tid']);
        // Save forum overview.
        $this->drupalGet('admin/structure/forum/');
        $this->submitForm([], 'Save');
        $this->assertSession()
            ->pageTextContains('The configuration options have been saved.');
        // Delete this second forum.
        $this->deleteForum($delete_forum['tid']);
        // Create forum at the top (root) level.
        $this->rootForum = $this->createForum('forum');
        // Test vocabulary form alterations.
        $this->drupalGet('admin/structure/taxonomy/manage/forums');
        $this->assertSession()
            ->buttonExists('Save');
        $this->assertSession()
            ->buttonNotExists('Delete');
        // Test term edit form alterations.
        $this->drupalGet('taxonomy/term/' . $this->forumContainer['tid'] . '/edit');
        // Test parent field been hidden by forum module.
        $this->assertSession()
            ->fieldNotExists('parent[]');
        // Create a default vocabulary named "Tags".
        $description = 'Use tags to group articles on similar topics into categories.';
        $help = 'Enter a comma-separated list of words to describe your content.';
        $vocabulary = Vocabulary::create([
            'name' => 'Tags',
            'description' => $description,
            'vid' => 'tags',
            'langcode' => \Drupal::languageManager()->getDefaultLanguage()
                ->getId(),
            'help' => $help,
        ]);
        $vocabulary->save();
        // Test tags vocabulary form is not affected.
        $this->drupalGet('admin/structure/taxonomy/manage/tags');
        $this->assertSession()
            ->buttonExists('Save');
        $this->assertSession()
            ->linkExists('Delete');
        // Test tags vocabulary term form is not affected.
        $this->drupalGet('admin/structure/taxonomy/manage/tags/add');
        $this->assertSession()
            ->fieldExists('parent[]');
        // Test relations widget exists.
        $this->assertSession()
            ->elementExists('xpath', "//details[@id='edit-relations']");
    }
    
    /**
     * Edits the forum taxonomy.
     */
    public function editForumVocabulary() {
        // Backup forum taxonomy.
        $vid = $this->config('forum.settings')
            ->get('vocabulary');
        $original_vocabulary = Vocabulary::load($vid);
        // Generate a random name and description.
        $edit = [
            'name' => $this->randomMachineName(10),
            'description' => $this->randomMachineName(100),
        ];
        // Edit the vocabulary.
        $this->drupalGet('admin/structure/taxonomy/manage/' . $original_vocabulary->id());
        $this->submitForm($edit, 'Save');
        $this->assertSession()
            ->statusCodeEquals(200);
        $this->assertSession()
            ->pageTextContains("Updated vocabulary {$edit['name']}.");
        // Grab the newly edited vocabulary.
        $current_vocabulary = Vocabulary::load($vid);
        // Make sure we actually edited the vocabulary properly.
        $this->assertEquals($edit['name'], $current_vocabulary->label(), 'The name was updated');
        $this->assertEquals($edit['description'], $current_vocabulary->getDescription(), 'The description was updated');
        // Restore the original vocabulary's name and description.
        $current_vocabulary->set('name', $original_vocabulary->label());
        $current_vocabulary->set('description', $original_vocabulary->getDescription());
        $current_vocabulary->save();
        // Reload vocabulary to make sure changes are saved.
        $current_vocabulary = Vocabulary::load($vid);
        $this->assertEquals($original_vocabulary->label(), $current_vocabulary->label(), 'The original vocabulary settings were restored');
    }
    
    /**
     * Creates a forum container or a forum.
     *
     * @param string $type
     *   The forum type (forum container or forum).
     * @param int $parent
     *   The forum parent. This defaults to 0, indicating a root forum.
     *
     * @return \Drupal\Core\Database\StatementInterface
     *   The created taxonomy term data.
     */
    public function createForum($type, $parent = 0) {
        // Generate a random name/description.
        $name = $this->randomMachineName(10);
        $description = $this->randomMachineName(100);
        $edit = [
            'name[0][value]' => $name,
            'description[0][value]' => $description,
            'parent[0]' => $parent,
            'weight' => '0',
        ];
        // Create forum.
        $this->drupalGet('admin/structure/forum/add/' . $type);
        $this->submitForm($edit, 'Save');
        $this->assertSession()
            ->statusCodeEquals(200);
        $type = $type == 'container' ? 'forum container' : 'forum';
        $this->assertSession()
            ->pageTextContains('Created new ' . $type . ' ' . $name . '.');
        // Verify that the creation message contains a link to a term.
        $this->assertSession()
            ->elementExists('xpath', '//div[@data-drupal-messages]//a[contains(@href, "term/")]');
        
        /** @var \Drupal\taxonomy\TermStorageInterface $taxonomy_term_storage */
        $taxonomy_term_storage = $this->container
            ->get('entity_type.manager')
            ->getStorage('taxonomy_term');
        // Verify forum.
        $term = $taxonomy_term_storage->loadByProperties([
            'vid' => $this->config('forum.settings')
                ->get('vocabulary'),
            'name' => $name,
            'description__value' => $description,
        ]);
        $term = array_shift($term);
        $this->assertNotEmpty($term, "The forum type '{$type}' should exist in the database.");
        // Verify forum hierarchy.
        $tid = $term->id();
        $parent_tid = $taxonomy_term_storage->loadParents($tid);
        $parent_tid = empty($parent_tid) ? 0 : array_shift($parent_tid)->id();
        $this->assertSame($parent, $parent_tid, 'The ' . $type . ' is linked to its container');
        $forum = $taxonomy_term_storage->load($tid);
        $this->assertEquals($type == 'forum container', (bool) $forum->forum_container->value);
        return [
            'tid' => $tid,
            'name' => $term->getName(),
            'vid' => $term->bundle(),
        ];
    }
    
    /**
     * Deletes a forum.
     *
     * @param int $tid
     *   The forum ID.
     */
    public function deleteForum($tid) {
        // Delete the forum.
        $this->drupalGet('admin/structure/forum/edit/forum/' . $tid);
        $this->clickLink('Delete');
        $this->assertSession()
            ->pageTextContains('Are you sure you want to delete the forum');
        $this->assertSession()
            ->pageTextNotContains('Add forum');
        $this->assertSession()
            ->pageTextNotContains('Add forum container');
        $this->submitForm([], 'Delete');
        // Assert that the forum no longer exists.
        $this->drupalGet('forum/' . $tid);
        $this->assertSession()
            ->statusCodeEquals(404);
    }
    
    /**
     * Runs basic tests on the indicated user.
     *
     * @param \Drupal\Core\Session\AccountInterface $user
     *   The logged in user.
     * @param bool $admin
     *   User has 'access administration pages' privilege.
     */
    private function doBasicTests($user, $admin) {
        // Log in the user.
        $this->drupalLogin($user);
        // Attempt to create forum topic under a container.
        $this->createForumTopic($this->forumContainer, TRUE);
        // Create forum node.
        $node = $this->createForumTopic($this->forum, FALSE);
        // Verify the user has access to all the forum nodes.
        $this->verifyForums($node, $admin);
    }
    
    /**
     * Tests a forum with a new post displays properly.
     */
    public function testForumWithNewPost() : void {
        // Log in as the first user.
        $this->drupalLogin($this->adminUser);
        // Create a forum container.
        $this->forumContainer = $this->createForum('container');
        // Create a forum.
        $this->forum = $this->createForum('forum');
        // Create a topic.
        $node = $this->createForumTopic($this->forum, FALSE);
        // Log in as a second user.
        $this->drupalLogin($this->postCommentUser);
        // Post a reply to the topic.
        $edit = [];
        $edit['subject[0][value]'] = $this->randomMachineName();
        $edit['comment_body[0][value]'] = $this->randomMachineName();
        $this->drupalGet('node/' . $node->id());
        $this->submitForm($edit, 'Save');
        $this->assertSession()
            ->statusCodeEquals(200);
        // Test adding a new comment.
        $this->clickLink('Add new comment');
        $this->assertSession()
            ->statusCodeEquals(200);
        $this->assertSession()
            ->fieldExists('comment_body[0][value]');
        // Log in as the first user.
        $this->drupalLogin($this->adminUser);
        // Check that forum renders properly.
        $this->drupalGet("forum/{$this->forum['tid']}");
        $this->assertSession()
            ->statusCodeEquals(200);
        // Verify there is no unintentional HTML tag escaping.
        $this->assertSession()
            ->assertNoEscaped('<');
    }
    
    /**
     * Creates a forum topic.
     *
     * @param array $forum
     *   A forum array.
     * @param bool $container
     *   TRUE if $forum is a container; FALSE otherwise.
     *
     * @return object|null
     *   The created topic node or NULL if the forum is a container.
     */
    public function createForumTopic($forum, $container = FALSE) {
        // Generate a random subject/body.
        $title = $this->randomMachineName(20);
        $body = $this->randomMachineName(200);
        $edit = [
            'title[0][value]' => $title,
            'body[0][value]' => $body,
        ];
        $tid = $forum['tid'];
        // Create the forum topic, preselecting the forum ID via a URL parameter.
        $this->drupalGet('node/add/forum', [
            'query' => [
                'forum_id' => $tid,
            ],
        ]);
        $this->submitForm($edit, 'Save');
        if ($container) {
            $this->assertSession()
                ->pageTextNotContains("Forum topic {$title} has been created.");
            $this->assertSession()
                ->pageTextContains("The item {$forum['name']} is a forum container, not a forum.");
            return;
        }
        else {
            $this->assertSession()
                ->pageTextContains("Forum topic {$title} has been created.");
            $this->assertSession()
                ->pageTextNotContains("The item {$forum['name']} is a forum container, not a forum.");
            // Verify that the creation message contains a link to a node.
            $this->assertSession()
                ->elementExists('xpath', '//div[@data-drupal-messages]//a[contains(@href, "node/")]');
        }
        // Retrieve node object, ensure that the topic was created and in the proper forum.
        $node = $this->drupalGetNodeByTitle($title);
        $this->assertNotNull($node, "Node {$title} was loaded");
        $this->assertEquals($tid, $node->taxonomy_forums->target_id, 'Saved forum topic was in the expected forum');
        // View forum topic.
        $this->drupalGet('node/' . $node->id());
        $this->assertSession()
            ->pageTextContains($title);
        $this->assertSession()
            ->pageTextContains($body);
        return $node;
    }
    
    /**
     * Verifies that the logged in user has access to a forum node.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node being checked.
     * @param bool $admin
     *   Boolean to indicate whether the user can 'access administration pages'.
     * @param int $response
     *   The expected HTTP response code.
     */
    private function verifyForums(EntityInterface $node, $admin, $response = 200) {
        $response2 = $admin ? 200 : 403;
        // View forum help node.
        $this->drupalGet('admin/help/forum');
        $this->assertSession()
            ->statusCodeEquals($response2);
        if ($response2 == 200) {
            $this->assertSession()
                ->titleEquals('Forum | Drupal');
            $this->assertSession()
                ->pageTextContains('Forum');
        }
        // View forum container page.
        $this->verifyForumView($this->forumContainer);
        // View forum page.
        $this->verifyForumView($this->forum, $this->forumContainer);
        // View root forum page.
        $this->verifyForumView($this->rootForum);
        // View forum node.
        $this->drupalGet('node/' . $node->id());
        $this->assertSession()
            ->statusCodeEquals(200);
        $this->assertSession()
            ->titleEquals($node->label() . ' | Drupal');
        $breadcrumb_build = [
            Link::createFromRoute('Home', '<front>'),
            Link::createFromRoute('Forums', 'forum.index'),
            Link::createFromRoute($this->forumContainer['name'], 'forum.page', [
                'taxonomy_term' => $this->forumContainer['tid'],
            ]),
            Link::createFromRoute($this->forum['name'], 'forum.page', [
                'taxonomy_term' => $this->forum['tid'],
            ]),
        ];
        $breadcrumb = [
            '#theme' => 'breadcrumb',
            '#links' => $breadcrumb_build,
        ];
        $this->assertSession()
            ->responseContains(\Drupal::service('renderer')->renderRoot($breadcrumb));
        // View forum edit node.
        $this->drupalGet('node/' . $node->id() . '/edit');
        $this->assertSession()
            ->statusCodeEquals($response);
        if ($response == 200) {
            $this->assertSession()
                ->titleEquals('Edit Forum topic ' . $node->label() . ' | Drupal');
        }
        if ($response == 200) {
            // Edit forum node (including moving it to another forum).
            $edit = [];
            $edit['title[0][value]'] = 'node/' . $node->id();
            $edit['body[0][value]'] = $this->randomMachineName(256);
            // Assume the topic is initially associated with $forum.
            $edit['taxonomy_forums'] = $this->rootForum['tid'];
            $edit['shadow'] = TRUE;
            $this->drupalGet('node/' . $node->id() . '/edit');
            $this->submitForm($edit, 'Save');
            $this->assertSession()
                ->pageTextContains('Forum topic ' . $edit['title[0][value]'] . ' has been updated.');
            // Verify topic was moved to a different forum.
            $forum_tid = $this->container
                ->get('database')
                ->select('forum', 'f')
                ->fields('f', [
                'tid',
            ])
                ->condition('nid', $node->id())
                ->condition('vid', $node->getRevisionId())
                ->execute()
                ->fetchField();
            $this->assertSame($this->rootForum['tid'], $forum_tid, 'The forum topic is linked to a different forum');
            // Delete forum node.
            $this->drupalGet('node/' . $node->id() . '/delete');
            $this->submitForm([], 'Delete');
            $this->assertSession()
                ->statusCodeEquals($response);
            $this->assertSession()
                ->pageTextContains("Forum topic {$edit['title[0][value]']} has been deleted.");
        }
    }
    
    /**
     * Verifies the display of a forum page.
     *
     * @param array $forum
     *   A row from the taxonomy_term_data table in an array.
     * @param array $parent
     *   (optional) An array representing the forum's parent.
     */
    private function verifyForumView($forum, $parent = NULL) {
        // View forum page.
        $this->drupalGet('forum/' . $forum['tid']);
        $this->assertSession()
            ->statusCodeEquals(200);
        $this->assertSession()
            ->titleEquals($forum['name'] . ' | Drupal');
        $breadcrumb_build = [
            Link::createFromRoute('Home', '<front>'),
            Link::createFromRoute('Forums', 'forum.index'),
        ];
        if (isset($parent)) {
            $breadcrumb_build[] = Link::createFromRoute($parent['name'], 'forum.page', [
                'taxonomy_term' => $parent['tid'],
            ]);
        }
        $breadcrumb = [
            '#theme' => 'breadcrumb',
            '#links' => $breadcrumb_build,
        ];
        $this->assertSession()
            ->responseContains(\Drupal::service('renderer')->renderRoot($breadcrumb));
    }
    
    /**
     * Generates forum topics.
     */
    private function generateForumTopics() {
        $this->nids = [];
        for ($i = 0; $i < 5; $i++) {
            $node = $this->createForumTopic($this->forum, FALSE);
            $this->nids[] = $node->id();
        }
    }
    
    /**
     * Evaluate whether "Add new Forum topic" button is present or not.
     */
    public function testForumTopicButton() : void {
        $this->drupalLogin($this->adminUser);
        // Validate that link doesn't exist on the forum container page.
        $forum_container = $this->createForum('container');
        $this->drupalGet('forum/' . $forum_container['tid']);
        $this->assertSession()
            ->linkNotExists('Add new Forum topic');
        // Validate that link exists on forum page.
        $forum = $this->createForum('forum');
        $this->drupalGet('forum/' . $forum['tid']);
        $this->assertSession()
            ->linkExists('Add new Forum topic');
    }

}