diff --git a/tests/src/Functional/ForumIndexUpdateTest.php b/tests/src/Functional/ForumIndexUpdateTest.php
index 8c2913f90c766e99da6816922527cd4f199571bf..1d0f401ba5c1c83931fbc1f5321ca9478944e25f 100644
--- a/tests/src/Functional/ForumIndexUpdateTest.php
+++ b/tests/src/Functional/ForumIndexUpdateTest.php
@@ -14,6 +14,11 @@ use Drupal\FunctionalTests\Update\UpdatePathTestBase;
  */
 final class ForumIndexUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/tests/src/Functional/migrate_drupal/d6/NoMultilingualReviewPageTest.php b/tests/src/Functional/migrate_drupal/d6/NoMultilingualReviewPageTest.php
index efe269284e8e2ee4838d912a9ccdc10d33f6e125..17e13cd8ea26bf66d9a3657c478533e2fa5e186c 100644
--- a/tests/src/Functional/migrate_drupal/d6/NoMultilingualReviewPageTest.php
+++ b/tests/src/Functional/migrate_drupal/d6/NoMultilingualReviewPageTest.php
@@ -11,6 +11,11 @@ use Drupal\Tests\migrate_drupal_ui\Functional\NoMultilingualReviewPageTestBase;
  */
 class NoMultilingualReviewPageTest extends NoMultilingualReviewPageTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/tests/src/Functional/migrate_drupal/d6/Upgrade6Test.php b/tests/src/Functional/migrate_drupal/d6/Upgrade6Test.php
index c18f5a0685c8033138d9be4cc7ddd29c7a2d11ab..554b8408b34261a823e90e9a4f9e8cbe80488890 100644
--- a/tests/src/Functional/migrate_drupal/d6/Upgrade6Test.php
+++ b/tests/src/Functional/migrate_drupal/d6/Upgrade6Test.php
@@ -15,6 +15,11 @@ use Drupal\Tests\migrate_drupal_ui\Functional\MigrateUpgradeExecuteTestBase;
  */
 class Upgrade6Test extends MigrateUpgradeExecuteTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/tests/src/Functional/migrate_drupal/d7/NoMultilingualReviewPageTest.php b/tests/src/Functional/migrate_drupal/d7/NoMultilingualReviewPageTest.php
index e541601cbe6722d286f7454bfdf1f7530529fbf3..7a8457de2fc00ef7904a97fcad0af5d0ab813551 100644
--- a/tests/src/Functional/migrate_drupal/d7/NoMultilingualReviewPageTest.php
+++ b/tests/src/Functional/migrate_drupal/d7/NoMultilingualReviewPageTest.php
@@ -13,6 +13,11 @@ use Drupal\Tests\migrate_drupal_ui\Functional\NoMultilingualReviewPageTestBase;
  */
 class NoMultilingualReviewPageTest extends NoMultilingualReviewPageTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/tests/src/Functional/migrate_drupal/d7/Upgrade7Test.php b/tests/src/Functional/migrate_drupal/d7/Upgrade7Test.php
index c0a519da85f31da7430fd46f37ee38a0d74dc682..bfb43449dd7d973b206e1b10b42f3524431df9eb 100644
--- a/tests/src/Functional/migrate_drupal/d7/Upgrade7Test.php
+++ b/tests/src/Functional/migrate_drupal/d7/Upgrade7Test.php
@@ -15,6 +15,11 @@ use Drupal\Tests\migrate_drupal_ui\Functional\MigrateUpgradeExecuteTestBase;
  */
 class Upgrade7Test extends MigrateUpgradeExecuteTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/tests/src/Unit/Breadcrumb/ForumBreadcrumbBuilderBaseTest.php b/tests/src/Unit/Breadcrumb/ForumBreadcrumbBuilderBaseTest.php
index 185455e9e03097e365d9e36aeccc9f9a5eeb452e..d41ffb6fde0f6fe207f250f6d111a68aafcc92a2 100644
--- a/tests/src/Unit/Breadcrumb/ForumBreadcrumbBuilderBaseTest.php
+++ b/tests/src/Unit/Breadcrumb/ForumBreadcrumbBuilderBaseTest.php
@@ -22,9 +22,7 @@ class ForumBreadcrumbBuilderBaseTest extends UnitTestCase {
   protected function setUp(): void {
     parent::setUp();
 
-    $cache_contexts_manager = $this->getMockBuilder('Drupal\Core\Cache\Context\CacheContextsManager')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $cache_contexts_manager = $this->createMock('Drupal\Core\Cache\Context\CacheContextsManager');
     $cache_contexts_manager->method('assertValidTokens')->willReturn(TRUE);
     $container = new Container();
     $container->set('cache_contexts_manager', $cache_contexts_manager);
@@ -75,13 +73,9 @@ class ForumBreadcrumbBuilderBaseTest extends UnitTestCase {
    */
   public function testBuild() {
     // Build all our dependencies, backwards.
-    $translation_manager = $this->getMockBuilder('Drupal\Core\StringTranslation\TranslationInterface')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $translation_manager = $this->createMock('Drupal\Core\StringTranslation\TranslationInterface');
 
-    $forum_manager = $this->getMockBuilder('Drupal\forum\ForumManagerInterface')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $forum_manager = $this->createMock('Drupal\forum\ForumManagerInterface');
 
     $prophecy = $this->prophesize('Drupal\taxonomy\VocabularyInterface');
     $prophecy->label()->willReturn('Fora_is_the_plural_of_forum');
diff --git a/tests/src/Unit/Breadcrumb/ForumListingBreadcrumbBuilderTest.php b/tests/src/Unit/Breadcrumb/ForumListingBreadcrumbBuilderTest.php
index 93bac6bea16d1092c7ecb9772928f43fbe40d1fd..8468a1d7833098df8d8944827445ba69ceffd95f 100644
--- a/tests/src/Unit/Breadcrumb/ForumListingBreadcrumbBuilderTest.php
+++ b/tests/src/Unit/Breadcrumb/ForumListingBreadcrumbBuilderTest.php
@@ -24,9 +24,7 @@ class ForumListingBreadcrumbBuilderTest extends UnitTestCase {
   protected function setUp(): void {
     parent::setUp();
 
-    $cache_contexts_manager = $this->getMockBuilder('Drupal\Core\Cache\Context\CacheContextsManager')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $cache_contexts_manager = $this->createMock('Drupal\Core\Cache\Context\CacheContextsManager');
     $cache_contexts_manager->method('assertValidTokens')->willReturn(TRUE);
     $container = new Container();
     $container->set('cache_contexts_manager', $cache_contexts_manager);
@@ -77,9 +75,7 @@ class ForumListingBreadcrumbBuilderTest extends UnitTestCase {
    */
   public function providerTestApplies() {
     // Send a Node mock, because NodeInterface cannot be mocked.
-    $mock_term = $this->getMockBuilder('Drupal\taxonomy\Entity\Term')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $mock_term = $this->createMock('Drupal\taxonomy\Entity\Term');
 
     return [
       [
@@ -115,9 +111,7 @@ class ForumListingBreadcrumbBuilderTest extends UnitTestCase {
    */
   public function testBuild() {
     // Build all our dependencies, backwards.
-    $translation_manager = $this->getMockBuilder('Drupal\Core\StringTranslation\TranslationInterface')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $translation_manager = $this->createMock('Drupal\Core\StringTranslation\TranslationInterface');
 
     $prophecy = $this->prophesize('Drupal\taxonomy\Entity\Term');
     $prophecy->label()->willReturn('Something');
@@ -135,7 +129,7 @@ class ForumListingBreadcrumbBuilderTest extends UnitTestCase {
     $prophecy->getCacheMaxAge()->willReturn(Cache::PERMANENT);
     $term2 = $prophecy->reveal();
 
-    $term_storage = $this->getMockBuilder(TermStorageInterface::class)->getMock();
+    $term_storage = $this->createMock(TermStorageInterface::class);
     $term_storage->expects($this->exactly(2))
       ->method('loadAllParents')
       ->willReturnOnConsecutiveCalls(
@@ -157,9 +151,7 @@ class ForumListingBreadcrumbBuilderTest extends UnitTestCase {
         ['forums', $prophecy->reveal()],
       ]);
 
-    $entity_type_manager = $this->getMockBuilder(EntityTypeManagerInterface::class)
-      ->disableOriginalConstructor()
-      ->getMock();
+    $entity_type_manager = $this->createMock(EntityTypeManagerInterface::class);
     $entity_type_manager->expects($this->any())
       ->method('getStorage')
       ->willReturnMap([
diff --git a/tests/src/Unit/Breadcrumb/ForumNodeBreadcrumbBuilderTest.php b/tests/src/Unit/Breadcrumb/ForumNodeBreadcrumbBuilderTest.php
index de013135980d4874743ae16b7ff032c83509768e..92eaa2ad8c372f9671156c65fa14e98743af19f0 100644
--- a/tests/src/Unit/Breadcrumb/ForumNodeBreadcrumbBuilderTest.php
+++ b/tests/src/Unit/Breadcrumb/ForumNodeBreadcrumbBuilderTest.php
@@ -24,9 +24,7 @@ class ForumNodeBreadcrumbBuilderTest extends UnitTestCase {
   protected function setUp(): void {
     parent::setUp();
 
-    $cache_contexts_manager = $this->getMockBuilder('Drupal\Core\Cache\Context\CacheContextsManager')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $cache_contexts_manager = $this->createMock('Drupal\Core\Cache\Context\CacheContextsManager');
     $cache_contexts_manager->method('assertValidTokens')->willReturn(TRUE);
     $container = new Container();
     $container->set('cache_contexts_manager', $cache_contexts_manager);
@@ -84,9 +82,7 @@ class ForumNodeBreadcrumbBuilderTest extends UnitTestCase {
    */
   public function providerTestApplies() {
     // Send a Node mock, because NodeInterface cannot be mocked.
-    $mock_node = $this->getMockBuilder('Drupal\node\Entity\Node')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $mock_node = $this->createMock('Drupal\node\Entity\Node');
 
     return [
       [
@@ -121,9 +117,7 @@ class ForumNodeBreadcrumbBuilderTest extends UnitTestCase {
    */
   public function testBuild() {
     // Build all our dependencies, backwards.
-    $translation_manager = $this->getMockBuilder('Drupal\Core\StringTranslation\TranslationInterface')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $translation_manager = $this->createMock('Drupal\Core\StringTranslation\TranslationInterface');
 
     $prophecy = $this->prophesize('Drupal\taxonomy\Entity\Term');
     $prophecy->label()->willReturn('Something');
@@ -141,10 +135,8 @@ class ForumNodeBreadcrumbBuilderTest extends UnitTestCase {
     $prophecy->getCacheMaxAge()->willReturn(Cache::PERMANENT);
     $term2 = $prophecy->reveal();
 
-    $forum_manager = $this->getMockBuilder('Drupal\forum\ForumManagerInterface')
-      ->disableOriginalConstructor()
-      ->getMock();
-    $term_storage = $this->getMockBuilder(TermStorageInterface::class)->getMock();
+    $forum_manager = $this->createMock('Drupal\forum\ForumManagerInterface');
+    $term_storage = $this->createMock(TermStorageInterface::class);
     $term_storage->expects($this->exactly(2))
       ->method('loadAllParents')
       ->willReturnOnConsecutiveCalls(
@@ -165,9 +157,7 @@ class ForumNodeBreadcrumbBuilderTest extends UnitTestCase {
         ['forums', $prophecy->reveal()],
       ]);
 
-    $entity_type_manager = $this->getMockBuilder(EntityTypeManagerInterface::class)
-      ->disableOriginalConstructor()
-      ->getMock();
+    $entity_type_manager = $this->createMock(EntityTypeManagerInterface::class);
     $entity_type_manager->expects($this->any())
       ->method('getStorage')
       ->willReturnMap([
@@ -194,9 +184,7 @@ class ForumNodeBreadcrumbBuilderTest extends UnitTestCase {
     $breadcrumb_builder->setStringTranslation($translation_manager);
 
     // The forum node we need a breadcrumb back from.
-    $forum_node = $this->getMockBuilder('Drupal\node\Entity\Node')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $forum_node = $this->createMock('Drupal\node\Entity\Node');
 
     // Our data set.
     $route_match = $this->createMock('Drupal\Core\Routing\RouteMatchInterface');
diff --git a/tests/src/Unit/ForumManagerTest.php b/tests/src/Unit/ForumManagerTest.php
index e61dcbf07f3b544068ce988eeeecfc584dbc3db6..54ec1b00cd36baf8fc0f35488f9d9c7e845dee54 100644
--- a/tests/src/Unit/ForumManagerTest.php
+++ b/tests/src/Unit/ForumManagerTest.php
@@ -21,15 +21,11 @@ class ForumManagerTest extends UnitTestCase {
     $entity_field_manager = $this->createMock(EntityFieldManagerInterface::class);
     $entity_type_manager = $this->createMock(EntityTypeManagerInterface::class);
 
-    $storage = $this->getMockBuilder('\Drupal\taxonomy\VocabularyStorage')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $storage = $this->createMock('\Drupal\taxonomy\VocabularyStorage');
 
     $config_factory = $this->createMock('\Drupal\Core\Config\ConfigFactoryInterface');
 
-    $config = $this->getMockBuilder('\Drupal\Core\Config\Config')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $config = $this->createMock('\Drupal\Core\Config\Config');
 
     $config_factory->expects($this->once())
       ->method('get')
@@ -50,17 +46,11 @@ class ForumManagerTest extends UnitTestCase {
       ->method('create')
       ->willReturn($term);
 
-    $connection = $this->getMockBuilder('\Drupal\Core\Database\Connection')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $connection = $this->createMock('\Drupal\Core\Database\Connection');
 
-    $translation_manager = $this->getMockBuilder('\Drupal\Core\StringTranslation\TranslationManager')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $translation_manager = $this->createMock('\Drupal\Core\StringTranslation\TranslationManager');
 
-    $comment_manager = $this->getMockBuilder('\Drupal\comment\CommentManagerInterface')
-      ->disableOriginalConstructor()
-      ->getMock();
+    $comment_manager = $this->createMock('\Drupal\comment\CommentManagerInterface');
 
     $manager = $this->getMockBuilder('\Drupal\forum\ForumManager')
       ->onlyMethods(['getChildren'])