diff --git a/core/modules/block/tests/src/Functional/BlockTest.php b/core/modules/block/tests/src/Functional/BlockTest.php
index e626f7e7f9fa..a71259ee3200 100644
--- a/core/modules/block/tests/src/Functional/BlockTest.php
+++ b/core/modules/block/tests/src/Functional/BlockTest.php
@@ -12,6 +12,7 @@ use Drupal\user\RoleInterface;
  * Tests basic block functionality.
  *
  * @group block
+ * @group #slow
  */
 class BlockTest extends BlockTestBase {
 
diff --git a/core/modules/block/tests/src/Functional/BlockUiTest.php b/core/modules/block/tests/src/Functional/BlockUiTest.php
index 28a4c476db9b..99f52a59d900 100644
--- a/core/modules/block/tests/src/Functional/BlockUiTest.php
+++ b/core/modules/block/tests/src/Functional/BlockUiTest.php
@@ -13,6 +13,7 @@ use Drupal\Tests\BrowserTestBase;
  * Tests that the block configuration UI exists and stores data correctly.
  *
  * @group block
+ * @group #slow
  */
 class BlockUiTest extends BrowserTestBase {
 
diff --git a/core/modules/media/tests/src/Functional/FieldFormatter/OEmbedFormatterTest.php b/core/modules/media/tests/src/Functional/FieldFormatter/OEmbedFormatterTest.php
index 8a382397d644..269160976d8c 100644
--- a/core/modules/media/tests/src/Functional/FieldFormatter/OEmbedFormatterTest.php
+++ b/core/modules/media/tests/src/Functional/FieldFormatter/OEmbedFormatterTest.php
@@ -13,6 +13,7 @@ use Drupal\Tests\media\Traits\OEmbedTestTrait;
  * @covers \Drupal\media\Plugin\Field\FieldFormatter\OEmbedFormatter
  *
  * @group media
+ * @group #slow
  */
 class OEmbedFormatterTest extends MediaFunctionalTestBase {
 
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonAnonTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonAnonTest.php
index 19aef9697a81..194a8da8fd17 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonAnonTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonAnonTest.php
@@ -6,6 +6,7 @@ use Drupal\Tests\rest\Functional\AnonResourceTestTrait;
 
 /**
  * @group rest
+ * @group #slow
  */
 class TermJsonAnonTest extends TermResourceTestBase {
 
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonCookieTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonCookieTest.php
index 6a721186a81e..fac344783c04 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonCookieTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonCookieTest.php
@@ -6,6 +6,7 @@ use Drupal\Tests\rest\Functional\CookieResourceTestTrait;
 
 /**
  * @group rest
+ * @group #slow
  */
 class TermJsonCookieTest extends TermResourceTestBase {
 
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlAnonTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlAnonTest.php
index ff05095d3d60..47db951445b2 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlAnonTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlAnonTest.php
@@ -7,6 +7,7 @@ use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrai
 
 /**
  * @group rest
+ * @group #slow
  */
 class TermXmlAnonTest extends TermResourceTestBase {
 
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlCookieTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlCookieTest.php
index a83fe821fdc0..9ffc97551422 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlCookieTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlCookieTest.php
@@ -7,6 +7,7 @@ use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrai
 
 /**
  * @group rest
+ * @group #slow
  */
 class TermXmlCookieTest extends TermResourceTestBase {
 
diff --git a/core/modules/views_ui/tests/src/Functional/DisplayTest.php b/core/modules/views_ui/tests/src/Functional/DisplayTest.php
index 5467baf0366d..ae46f6abf2ca 100644
--- a/core/modules/views_ui/tests/src/Functional/DisplayTest.php
+++ b/core/modules/views_ui/tests/src/Functional/DisplayTest.php
@@ -9,6 +9,7 @@ use Drupal\views\Views;
  * Tests the display UI.
  *
  * @group views_ui
+ * @group #slow
  */
 class DisplayTest extends UITestBase {