diff --git a/core/modules/jsonapi/tests/src/Kernel/TestCoverageTest.php b/core/modules/jsonapi/tests/src/Kernel/TestCoverageTest.php
index 09670e5e2223520e8ac8c799b34f43d46c4de118..7fbfd6b32452311c3759ca964f32ab69646c868d 100644
--- a/core/modules/jsonapi/tests/src/Kernel/TestCoverageTest.php
+++ b/core/modules/jsonapi/tests/src/Kernel/TestCoverageTest.php
@@ -14,6 +14,7 @@
  * Checks that all core content/config entity types have JSON:API test coverage.
  *
  * @group jsonapi
+ * @group #slow
  */
 class TestCoverageTest extends KernelTestBase {
 
diff --git a/core/tests/Drupal/KernelTests/Core/Extension/ModuleConfigureRouteTest.php b/core/tests/Drupal/KernelTests/Core/Extension/ModuleConfigureRouteTest.php
index 17d93ccdb0ddea925b540d2c596178cce06c6beb..681f54402edb1a9ccaf5d2dd7db31bd39a5dc6e2 100644
--- a/core/tests/Drupal/KernelTests/Core/Extension/ModuleConfigureRouteTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Extension/ModuleConfigureRouteTest.php
@@ -12,6 +12,7 @@
  * Tests the configure route for core modules.
  *
  * @group Module
+ * @group #slow
  */
 class ModuleConfigureRouteTest extends KernelTestBase {
 
diff --git a/core/tests/Drupal/KernelTests/Core/Theme/Stable9LibraryOverrideTest.php b/core/tests/Drupal/KernelTests/Core/Theme/Stable9LibraryOverrideTest.php
index 9d900ebcb2a4e70244471ce227ae27169ea23622..e793a13e5fec663803119b2966fa262fb8e6197e 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/Stable9LibraryOverrideTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/Stable9LibraryOverrideTest.php
@@ -8,6 +8,7 @@
  * Tests Stable 9's library overrides.
  *
  * @group Theme
+ * @group #slow
  */
 class Stable9LibraryOverrideTest extends StableLibraryOverrideTestBase {