diff -u b/core/modules/forum/tests/src/Functional/ForumTest.php b/core/modules/forum/tests/src/Functional/ForumTest.php
--- b/core/modules/forum/tests/src/Functional/ForumTest.php
+++ b/core/modules/forum/tests/src/Functional/ForumTest.php
@@ -137,7 +137,7 @@
     // Check that the basic forum install creates a default forum topic
     $this->drupalGet('/forum');
     // Look for the "General discussion" default forum
-    $this->assertRaw(Link::createFromRoute(t('General discussion'), 'forum.page', ['taxonomy_term' => 1])->toString(), "Found the default forum at the /forum listing");
+    $this->assertRaw(Link::createFromRoute($this->t('General discussion'), 'forum.page', ['taxonomy_term' => 1])->toString(), "Found the default forum at the /forum listing");
     // Check the presence of expected cache tags.
     $this->assertSession()->responseHeaderContains('X-Drupal-Cache-Tags', 'config:forum.settings');
 
@@ -173,7 +173,7 @@
     $this->drupalLogin($this->webUser);
     // Verify that this user is shown a message that they may not post content.
     $this->drupalGet('forum/' . $this->forum['tid']);
-    $this->assertText(t('You are not allowed to post new content in the forum'), "Authenticated user without permission to post forum content is shown message in local tasks to that effect.");
+    $this->assertText($this->t('You are not allowed to post new content in the forum'), "Authenticated user without permission to post forum content is shown message in local tasks to that effect.");
 
     // Log in, and do basic tests for a user with permission to edit any forum
     // content.
@@ -191,9 +191,9 @@
 
     // Verify that this user is shown a local task to add new forum content.
     $this->drupalGet('forum');
-    $this->assertSession()->linkExists(t('Add new Forum topic'));
+    $this->assertSession()->linkExists($this->t('Add new Forum topic'));
     $this->drupalGet('forum/' . $this->forum['tid']);
-    $this->assertSession()->linkExists(t('Add new Forum topic'));
+    $this->assertSession()->linkExists($this->t('Add new Forum topic'));
 
     // Log in a user with permission to edit any forum content.
     $this->drupalLogin($this->editAnyTopicsUser);
@@ -231,7 +231,7 @@
       'create forum content',
       'post comments',
     ]));
-    $this->drupalPostForm('admin/structure/types/manage/forum', ['options[promote]' => 'promote'], t('Save content type'));
+    $this->drupalPostForm('admin/structure/types/manage/forum', ['options[promote]' => 'promote'], $this->t('Save content type'));
     $this->createForumTopic($this->forum, FALSE);
     $this->createForumTopic($this->forum, FALSE);
     $this->drupalGet('node');
@@ -240,13 +240,13 @@
     $node = $this->createForumTopic($this->forum, FALSE);
     $edit = [];
     $edit['comment_body[0][value]'] = $this->randomMachineName();
-    $this->drupalPostForm('node/' . $node->id(), $edit, t('Save'));
+    $this->drupalPostForm('node/' . $node->id(), $edit, $this->t('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->drupalPostForm('node/' . $node->id() . '/edit', [], t('Save'));
+    $this->drupalPostForm('node/' . $node->id() . '/edit', [], $this->t('Save'));
     $this->assertSession()->statusCodeEquals(200);
 
     // Test the root forum page title change.
@@ -262,7 +262,7 @@
     // Test anonymous action link.
     $this->drupalLogout();
     $this->drupalGet('forum/' . $this->forum['tid']);
-    $this->assertSession()->linkExists(t('Log in to post new content in the forum.'));
+    $this->assertSession()->linkExists($this->t('Log in to post new content in the forum.'));
   }
 
   /**
@@ -286,7 +286,7 @@
     $edit['title[0][value]'] = $this->randomMachineName(10);
     $edit['body[0][value]'] = $this->randomMachineName(120);
     $this->drupalLogin($this->adminUser);
-    $this->drupalPostForm('node/add/forum', $edit, t('Save'));
+    $this->drupalPostForm('node/add/forum', $edit, $this->t('Save'));
 
     $nid_count = $this->container->get('entity_type.manager')
       ->getStorage('node')
@@ -312,7 +312,7 @@
 
     // Add forum to the Tools menu.
     $edit = [];
-    $this->drupalPostForm('admin/structure/menu/manage/tools', $edit, t('Save'));
+    $this->drupalPostForm('admin/structure/menu/manage/tools', $edit, $this->t('Save'));
     $this->assertSession()->statusCodeEquals(200);
 
     // Edit forum taxonomy.
@@ -323,7 +323,7 @@
     // Verify "edit container" link exists and functions correctly.
     $this->drupalGet('admin/structure/forum');
     // Verify help text is shown.
-    $this->assertText(t('Forums contain forum topics. Use containers to group related forums'));
+    $this->assertText($this->t('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');
@@ -340,8 +340,8 @@
     // Create second forum in container, destined to be deleted below.
     $delete_forum = $this->createForum('forum', $this->forumContainer['tid']);
     // Save forum overview.
-    $this->drupalPostForm('admin/structure/forum/', [], t('Save'));
-    $this->assertRaw(t('The configuration options have been saved.'));
+    $this->drupalPostForm('admin/structure/forum/', [], $this->t('Save'));
+    $this->assertRaw($this->t('The configuration options have been saved.'));
     // Delete this second forum.
     $this->deleteForum($delete_forum['tid']);
     // Create forum at the top (root) level.
@@ -371,7 +371,7 @@
     // Test tags vocabulary form is not affected.
     $this->drupalGet('admin/structure/taxonomy/manage/tags');
     $this->assertSession()->buttonExists('Save');
-    $this->assertSession()->linkExists(t('Delete'));
+    $this->assertSession()->linkExists($this->t('Delete'));
     // Test tags vocabulary term form is not affected.
     $this->drupalGet('admin/structure/taxonomy/manage/tags/add');
     $this->assertSession()->fieldExists('parent[]');
@@ -395,9 +395,9 @@
     ];
 
     // Edit the vocabulary.
-    $this->drupalPostForm('admin/structure/taxonomy/manage/' . $original_vocabulary->id(), $edit, t('Save'));
+    $this->drupalPostForm('admin/structure/taxonomy/manage/' . $original_vocabulary->id(), $edit, $this->t('Save'));
     $this->assertSession()->statusCodeEquals(200);
-    $this->assertRaw(t('Updated vocabulary %name.', ['%name' => $edit['name']]), 'Vocabulary was edited');
+    $this->assertRaw($this->t('Updated vocabulary %name.', ['%name' => $edit['name']]), 'Vocabulary was edited');
 
     // Grab the newly edited vocabulary.
     $current_vocabulary = Vocabulary::load($vid);
@@ -439,13 +439,13 @@
     ];
 
     // Create forum.
-    $this->drupalPostForm('admin/structure/forum/add/' . $type, $edit, t('Save'));
+    $this->drupalPostForm('admin/structure/forum/add/' . $type, $edit, $this->t('Save'));
     $this->assertSession()->statusCodeEquals(200);
     $type = ($type == 'container') ? 'forum container' : 'forum';
     $this->assertText(
       t(
         'Created new @type @term.',
-        ['@term' => $name, '@type' => t($type)]
+        ['@term' => $name, '@type' => $this->t($type)]
       ),
       new FormattableMarkup('@type was created', ['@type' => ucfirst($type)])
     );
@@ -489,11 +489,11 @@
   public function deleteForum($tid) {
     // Delete the forum.
     $this->drupalGet('admin/structure/forum/edit/forum/' . $tid);
-    $this->clickLink(t('Delete'));
+    $this->clickLink($this->t('Delete'));
     $this->assertText('Are you sure you want to delete the forum');
     $this->assertNoText('Add forum');
     $this->assertNoText('Add forum container');
-    $this->drupalPostForm(NULL, [], t('Delete'));
+    $this->drupalPostForm(NULL, [], $this->t('Delete'));
 
     // Assert that the forum no longer exists.
     $this->drupalGet('forum/' . $tid);
@@ -538,7 +538,7 @@
     $edit = [];
     $edit['subject[0][value]'] = $this->randomMachineName();
     $edit['comment_body[0][value]'] = $this->randomMachineName();
-    $this->drupalPostForm('node/' . $node->id(), $edit, t('Save'));
+    $this->drupalPostForm('node/' . $node->id(), $edit, $this->t('Save'));
     $this->assertSession()->statusCodeEquals(200);
 
     // Test replying to a comment.
@@ -579,17 +579,17 @@
     $tid = $forum['tid'];
 
     // Create the forum topic, preselecting the forum ID via a URL parameter.
-    $this->drupalPostForm('node/add/forum', $edit, t('Save'), ['query' => ['forum_id' => $tid]]);
+    $this->drupalPostForm('node/add/forum', $edit, $this->t('Save'), ['query' => ['forum_id' => $tid]]);
 
-    $type = t('Forum topic');
+    $type = $this->t('Forum topic');
     if ($container) {
-      $this->assertNoText(t('@type @title has been created.', ['@type' => $type, '@title' => $title]), 'Forum topic was not created');
-      $this->assertRaw(t('The item %title is a forum container, not a forum.', ['%title' => $forum['name']]), 'Error message was shown');
+      $this->assertNoText($this->t('@type @title has been created.', ['@type' => $type, '@title' => $title]), 'Forum topic was not created');
+      $this->assertRaw($this->t('The item %title is a forum container, not a forum.', ['%title' => $forum['name']]), 'Error message was shown');
       return;
     }
     else {
-      $this->assertText(t('@type @title has been created.', ['@type' => $type, '@title' => $title]), 'Forum topic was created');
-      $this->assertNoRaw(t('The item %title is a forum container, not a forum.', ['%title' => $forum['name']]), 'No error message was shown');
+      $this->assertText($this->t('@type @title has been created.', ['@type' => $type, '@title' => $title]), 'Forum topic was created');
+      $this->assertNoRaw($this->t('The item %title is a forum container, not a forum.', ['%title' => $forum['name']]), 'No error message was shown');
 
       // Verify that the creation message contains a link to a term.
       $view_link = $this->xpath('//div[@class="messages"]//a[contains(@href, :href)]', [':href' => 'term/']);
@@ -627,7 +627,7 @@
     $this->assertSession()->statusCodeEquals($response2);
     if ($response2 == 200) {
       $this->assertSession()->titleEquals('Forum | Drupal');
-      $this->assertText(t('Forum'), 'Forum help node was displayed');
+      $this->assertText($this->t('Forum'), 'Forum help node was displayed');
     }
 
     // View forum container page.
@@ -668,8 +668,8 @@
       // Assume the topic is initially associated with $forum.
       $edit['taxonomy_forums'] = $this->rootForum['tid'];
       $edit['shadow'] = TRUE;
-      $this->drupalPostForm('node/' . $node->id() . '/edit', $edit, t('Save'));
-      $this->assertText(t('Forum topic @title has been updated.', ['@title' => $edit['title[0][value]']]), 'Forum node was edited');
+      $this->drupalPostForm('node/' . $node->id() . '/edit', $edit, $this->t('Save'));
+      $this->assertText($this->t('Forum topic @title has been updated.', ['@title' => $edit['title[0][value]']]), 'Forum node was edited');
 
       // Verify topic was moved to a different forum.
       $forum_tid = $this->container
@@ -683,9 +683,9 @@
       $this->assertTrue($forum_tid == $this->rootForum['tid'], 'The forum topic is linked to a different forum');
 
       // Delete forum node.
-      $this->drupalPostForm('node/' . $node->id() . '/delete', [], t('Delete'));
+      $this->drupalPostForm('node/' . $node->id() . '/delete', [], $this->t('Delete'));
       $this->assertSession()->statusCodeEquals($response);
-      $this->assertRaw(t('Forum topic %title has been deleted.', ['%title' => $edit['title[0][value]']]), 'Forum node was deleted');
+      $this->assertRaw($this->t('Forum topic %title has been deleted.', ['%title' => $edit['title[0][value]']]), 'Forum node was deleted');
     }
   }
 
diff -u b/core/modules/forum/tests/src/Functional/ForumUninstallTest.php b/core/modules/forum/tests/src/Functional/ForumUninstallTest.php
--- b/core/modules/forum/tests/src/Functional/ForumUninstallTest.php
+++ b/core/modules/forum/tests/src/Functional/ForumUninstallTest.php
@@ -83,7 +83,7 @@
     $this->assertText('To uninstall Forum, first delete all Forum content');
 
     // Delete the node.
-    $this->drupalPostForm('node/' . $node->id() . '/delete', [], t('Delete'));
+    $this->drupalPostForm('node/' . $node->id() . '/delete', [], $this->t('Delete'));
 
     // Attempt to uninstall forum.
     $this->drupalGet('admin/modules/uninstall');
@@ -99,7 +99,7 @@
 
     // Ensure that the forum node type can not be deleted.
     $this->drupalGet('admin/structure/types/manage/forum');
-    $this->assertSession()->linkNotExists(t('Delete'));
+    $this->assertSession()->linkNotExists($this->t('Delete'));
 
     // Now attempt to uninstall forum.
     $this->drupalGet('admin/modules/uninstall');
@@ -107,8 +107,8 @@
     $this->assertFieldByName('uninstall[forum]');
     $this->drupalPostForm('admin/modules/uninstall', [
       'uninstall[forum]' => 1,
-    ], t('Uninstall'));
-    $this->drupalPostForm(NULL, [], t('Uninstall'));
+    ], $this->t('Uninstall'));
+    $this->drupalPostForm(NULL, [], $this->t('Uninstall'));
 
     // Check that the field is now deleted.
     $field_storage = FieldStorageConfig::loadByName('node', 'taxonomy_forums');
@@ -121,11 +121,11 @@
       'title_label' => 'title for forum',
       'type' => 'forum',
     ];
-    $this->drupalPostForm('admin/structure/types/add', $edit, t('Save content type'));
+    $this->drupalPostForm('admin/structure/types/add', $edit, $this->t('Save content type'));
     $this->assertTrue((bool) NodeType::load('forum'), 'Node type with machine forum created.');
     $this->drupalGet('admin/structure/types/manage/forum');
-    $this->clickLink(t('Delete'));
-    $this->drupalPostForm(NULL, [], t('Delete'));
+    $this->clickLink($this->t('Delete'));
+    $this->drupalPostForm(NULL, [], $this->t('Delete'));
     $this->assertSession()->statusCodeEquals(200);
     $this->assertFalse((bool) NodeType::load('forum'), 'Node type with machine forum deleted.');
 
only in patch2:
unchanged:
--- a/core/modules/forum/tests/src/Functional/ForumBlockTest.php
+++ b/core/modules/forum/tests/src/Functional/ForumBlockTest.php
@@ -58,7 +58,7 @@ public function testNewForumTopicsBlock() {
     // Create 5 forum topics.
     $topics = $this->createForumTopics();
 
-    $this->assertSession()->linkExists(t('More'), 0, 'New forum topics block has a "more"-link.');
+    $this->assertSession()->linkExists($this->t('More'), 0, 'New forum topics block has a "more"-link.');
     $this->assertLinkByHref('forum', 0, 'New forum topics block has a "more"-link.');
 
     // We expect all 5 forum topics to appear in the "New forum topics" block.
@@ -113,7 +113,7 @@ public function testActiveForumTopicsBlock() {
     // Enable the block.
     $block = $this->drupalPlaceBlock('forum_active_block');
     $this->drupalGet('');
-    $this->assertSession()->linkExists(t('More'), 0, 'Active forum topics block has a "more"-link.');
+    $this->assertSession()->linkExists($this->t('More'), 0, 'Active forum topics block has a "more"-link.');
     $this->assertLinkByHref('forum', 0, 'Active forum topics block has a "more"-link.');
 
     // We expect the first 5 forum topics to appear in the "Active forum topics"
@@ -175,7 +175,7 @@ protected function createForumTopics($count = 5) {
       ];
 
       // Create the forum topic, preselecting the forum ID via a URL parameter.
-      $this->drupalPostForm('node/add/forum', $edit, t('Save'), ['query' => ['forum_id' => 1]]);
+      $this->drupalPostForm('node/add/forum', $edit, $this->t('Save'), ['query' => ['forum_id' => 1]]);
       $topics[] = $title;
     }
 
only in patch2:
unchanged:
--- a/core/modules/forum/tests/src/Functional/ForumIndexTest.php
+++ b/core/modules/forum/tests/src/Functional/ForumIndexTest.php
@@ -53,9 +53,9 @@ public function testForumIndexStatus() {
 
     // Create the forum topic, preselecting the forum ID via a URL parameter.
     $this->drupalGet("forum/$tid");
-    $this->clickLink(t('Add new @node_type', ['@node_type' => 'Forum topic']));
+    $this->clickLink($this->t('Add new @node_type', ['@node_type' => 'Forum topic']));
     $this->assertUrl("node/add/forum?forum_id=$tid");
-    $this->drupalPostForm(NULL, $edit, t('Save'));
+    $this->drupalPostForm(NULL, $edit, $this->t('Save'));
 
     // Check that the node exists in the database.
     $node = $this->drupalGetNodeByTitle($title);
@@ -67,8 +67,8 @@ public function testForumIndexStatus() {
       'description[0][value]' => $this->randomMachineName(200),
       'parent[0]' => $tid,
     ];
-    $this->drupalPostForm('admin/structure/forum/add/forum', $edit, t('Save'));
-    $this->assertSession()->linkExists(t('edit forum'));
+    $this->drupalPostForm('admin/structure/forum/add/forum', $edit, $this->t('Save'));
+    $this->assertSession()->linkExists($this->t('edit forum'));
 
     $tid_child = $tid + 1;
 
@@ -84,9 +84,9 @@ public function testForumIndexStatus() {
 
     // Unpublish the node.
     $edit = ['status[value]' => FALSE];
-    $this->drupalPostForm('node/' . $node->id() . '/edit', $edit, t('Save'));
+    $this->drupalPostForm('node/' . $node->id() . '/edit', $edit, $this->t('Save'));
     $this->drupalGet('node/' . $node->id());
-    $this->assertText(t('Access denied'), 'Unpublished node is no longer accessible.');
+    $this->assertText($this->t('Access denied'), 'Unpublished node is no longer accessible.');
 
     // Verify that the node no longer appears on the index.
     $this->drupalGet('forum/' . $tid);
only in patch2:
unchanged:
--- a/core/modules/forum/tests/src/Functional/ForumNodeAccessTest.php
+++ b/core/modules/forum/tests/src/Functional/ForumNodeAccessTest.php
@@ -65,7 +65,7 @@ public function testForumNodeAccess() {
       'body[0][value]' => $this->randomMachineName(200),
       'private[0][value]' => TRUE,
     ];
-    $this->drupalPostForm('node/add/forum', $edit, t('Save'), ['query' => ['forum_id' => 1]]);
+    $this->drupalPostForm('node/add/forum', $edit, $this->t('Save'), ['query' => ['forum_id' => 1]]);
     $private_node = $this->drupalGetNodeByTitle($private_node_title);
     $this->assertTrue(!empty($private_node), 'New private forum node found in database.');
 
@@ -75,7 +75,7 @@ public function testForumNodeAccess() {
       'title[0][value]' => $public_node_title,
       'body[0][value]' => $this->randomMachineName(200),
     ];
-    $this->drupalPostForm('node/add/forum', $edit, t('Save'), ['query' => ['forum_id' => 1]]);
+    $this->drupalPostForm('node/add/forum', $edit, $this->t('Save'), ['query' => ['forum_id' => 1]]);
     $public_node = $this->drupalGetNodeByTitle($public_node_title);
     $this->assertTrue(!empty($public_node), 'New public forum node found in database.');