diff --git a/core/modules/content_moderation/tests/src/Functional/ModerationLocaleTest.php b/core/modules/content_moderation/tests/src/Functional/ModerationLocaleTest.php
index e13127cb72ab30e60ef5d54f98644c99357e427b..3e264f24fbfe7540feb551f2a0f9b96055564096 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModerationLocaleTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModerationLocaleTest.php
@@ -8,6 +8,7 @@
  * Test content_moderation functionality with localization and translation.
  *
  * @group content_moderation
+ * @group #slow
  */
 class ModerationLocaleTest extends ModerationStateTestBase {
 
diff --git a/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTest.php b/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTest.php
index 6b39d4ea67f4b5dcd9c333d68592cfccd3669853..cdaeae93a4827a0c30a8821bc8cb3f7c6d27ba32 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTest.php
@@ -9,6 +9,7 @@
  * Tests general content moderation workflow for nodes.
  *
  * @group content_moderation
+ * @group #slow
  */
 class ModerationStateNodeTest extends ModerationStateTestBase {
 
diff --git a/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTypeTest.php b/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTypeTest.php
index 66b22ab3901eefcfcb6f2890849bf0870eb35731..437242af15e3bf6cf8d8c0c2bf3f981c28fe8c87 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTypeTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTypeTest.php
@@ -6,6 +6,7 @@
  * Tests moderation state node type integration.
  *
  * @group content_moderation
+ * @group #slow
  */
 class ModerationStateNodeTypeTest extends ModerationStateTestBase {
 
diff --git a/core/modules/content_moderation/tests/src/Functional/ViewsModerationStateFilterTest.php b/core/modules/content_moderation/tests/src/Functional/ViewsModerationStateFilterTest.php
index bc5cbb56a82f774e086acd37cb24f6906b2b9218..cdaae0d2e41f115bbf21aac7b878c4c8e8915f81 100644
--- a/core/modules/content_moderation/tests/src/Functional/ViewsModerationStateFilterTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ViewsModerationStateFilterTest.php
@@ -14,6 +14,7 @@
  * @coversDefaultClass \Drupal\content_moderation\Plugin\views\filter\ModerationStateFilter
  *
  * @group content_moderation
+ * @group #slow
  */
 class ViewsModerationStateFilterTest extends ViewTestBase {
 
diff --git a/core/modules/forum/tests/src/Functional/migrate_drupal/d6/Upgrade6Test.php b/core/modules/forum/tests/src/Functional/migrate_drupal/d6/Upgrade6Test.php
index f8ba9e6f9b61bb9b5d5cf74b26a0d93124303048..fa0303026fdcd38ec1f753b6a7b2e7bd3959fd58 100644
--- a/core/modules/forum/tests/src/Functional/migrate_drupal/d6/Upgrade6Test.php
+++ b/core/modules/forum/tests/src/Functional/migrate_drupal/d6/Upgrade6Test.php
@@ -10,6 +10,7 @@
  * The test method is provided by the MigrateUpgradeTestBase class.
  *
  * @group forum
+ * @group #slow
  */
 class Upgrade6Test extends MigrateUpgradeExecuteTestBase {
 
diff --git a/core/modules/forum/tests/src/Functional/migrate_drupal/d7/Upgrade7Test.php b/core/modules/forum/tests/src/Functional/migrate_drupal/d7/Upgrade7Test.php
index df6180b495d451e452ab66f6eaeffba336e1c917..2ff0f78bd4e60abdfc1a621b3c408f97fc5654b8 100644
--- a/core/modules/forum/tests/src/Functional/migrate_drupal/d7/Upgrade7Test.php
+++ b/core/modules/forum/tests/src/Functional/migrate_drupal/d7/Upgrade7Test.php
@@ -10,6 +10,7 @@
  * The test method is provided by the MigrateUpgradeTestBase class.
  *
  * @group forum
+ * @group #slow
  */
 class Upgrade7Test extends MigrateUpgradeExecuteTestBase {
 
diff --git a/core/modules/image/tests/src/Functional/ImageAdminStylesTest.php b/core/modules/image/tests/src/Functional/ImageAdminStylesTest.php
index d62f0a0e3d94396c6ecb072bf81513522bc0538c..e0c9e671f51c00ea7fcb113b78e2e79281e8dcb0 100644
--- a/core/modules/image/tests/src/Functional/ImageAdminStylesTest.php
+++ b/core/modules/image/tests/src/Functional/ImageAdminStylesTest.php
@@ -15,6 +15,7 @@
  * Tests creation, deletion, and editing of image styles and effects.
  *
  * @group image
+ * @group #slow
  */
 class ImageAdminStylesTest extends ImageFieldTestBase {
 
diff --git a/core/modules/image/tests/src/Functional/ImageFieldDisplayTest.php b/core/modules/image/tests/src/Functional/ImageFieldDisplayTest.php
index 6517f377319fe86a55c8df5c31b2a27068cfc313..8cef396210f5dc5e9866cf37a5b72ce647bb0fa3 100644
--- a/core/modules/image/tests/src/Functional/ImageFieldDisplayTest.php
+++ b/core/modules/image/tests/src/Functional/ImageFieldDisplayTest.php
@@ -15,6 +15,7 @@
  * Tests the display of image fields.
  *
  * @group image
+ * @group #slow
  */
 class ImageFieldDisplayTest extends ImageFieldTestBase {
 
diff --git a/core/modules/image/tests/src/Functional/ImageFieldValidateTest.php b/core/modules/image/tests/src/Functional/ImageFieldValidateTest.php
index b426730dd7f126d793b8ad29aefe50c2b2dd5f3b..e7444aa0059cfdbf4f9af45de88bc1be47d49153 100644
--- a/core/modules/image/tests/src/Functional/ImageFieldValidateTest.php
+++ b/core/modules/image/tests/src/Functional/ImageFieldValidateTest.php
@@ -9,6 +9,7 @@
  * Tests validation functions such as min/max dimensions.
  *
  * @group image
+ * @group #slow
  */
 class ImageFieldValidateTest extends ImageFieldTestBase {
 
diff --git a/core/modules/options/tests/src/FunctionalJavascript/OptionsFieldUITest.php b/core/modules/options/tests/src/FunctionalJavascript/OptionsFieldUITest.php
index ad7967369bfcfd2e80885d8fe955fed3c5c7f53e..02c099fcbe50853ce3f5d99d2c88e43ca15e3069 100644
--- a/core/modules/options/tests/src/FunctionalJavascript/OptionsFieldUITest.php
+++ b/core/modules/options/tests/src/FunctionalJavascript/OptionsFieldUITest.php
@@ -13,6 +13,7 @@
  * Tests the Options field UI functionality.
  *
  * @group options
+ * @group #slow
  */
 class OptionsFieldUITest extends WebDriverTestBase {
 
diff --git a/core/modules/system/tests/src/Functional/Theme/ThemeUiTest.php b/core/modules/system/tests/src/Functional/Theme/ThemeUiTest.php
index 4be6b94fa0f82ae7069254c16fd77c4fde77e35d..2b85faaf72ae882c9a0c9075e3e0c2a028160e38 100644
--- a/core/modules/system/tests/src/Functional/Theme/ThemeUiTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/ThemeUiTest.php
@@ -9,6 +9,7 @@
  * Tests the theme UI.
  *
  * @group Theme
+ * @group #slow
  */
 class ThemeUiTest extends BrowserTestBase {
 
diff --git a/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBaseTest.php b/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBaseTest.php
index 0e0f772a3cb7ab0bb0e7d43c7be41ed0878b73e9..83a025b54e77ec9430845c0cc80cc3f40a4425e9 100644
--- a/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBaseTest.php
+++ b/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBaseTest.php
@@ -11,6 +11,7 @@
  * Tests the update path base class.
  *
  * @group Update
+ * @group #slow
  */
 class UpdatePathTestBaseTest extends UpdatePathTestBase {