diff --git a/core/modules/block/src/Tests/Views/DisplayBlockTest.php b/core/modules/block/src/Tests/Views/DisplayBlockTest.php
index 3d3584579a..5ff324c1fd 100644
--- a/core/modules/block/src/Tests/Views/DisplayBlockTest.php
+++ b/core/modules/block/src/Tests/Views/DisplayBlockTest.php
@@ -4,7 +4,7 @@
 
 use Drupal\Component\Serialization\Json;
 use Drupal\Core\Url;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\views\Entity\View;
 use Drupal\views\Views;
 use Drupal\views\Tests\ViewTestBase;
diff --git a/core/modules/comment/src/Tests/CommentRssTest.php b/core/modules/comment/src/Tests/CommentRssTest.php
index 35cad71fa9..6df3ad11dc 100644
--- a/core/modules/comment/src/Tests/CommentRssTest.php
+++ b/core/modules/comment/src/Tests/CommentRssTest.php
@@ -5,7 +5,7 @@
 use Drupal\comment\Plugin\Field\FieldType\CommentItemInterface;
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Entity\Entity\EntityViewDisplay;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 
 /**
  * Tests comments as part of an RSS feed.
diff --git a/core/modules/contact/tests/src/Functional/ContactPersonalTest.php b/core/modules/contact/tests/src/Functional/ContactPersonalTest.php
index 7e6ecad7cd..5f6e8e6ad2 100644
--- a/core/modules/contact/tests/src/Functional/ContactPersonalTest.php
+++ b/core/modules/contact/tests/src/Functional/ContactPersonalTest.php
@@ -6,8 +6,8 @@
 use Drupal\Component\Render\PlainTextOutput;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\Test\AssertMailTrait;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\Tests\BrowserTestBase;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\user\RoleInterface;
 
 /**
diff --git a/core/modules/content_translation/src/Tests/ContentTranslationUITestBase.php b/core/modules/content_translation/src/Tests/ContentTranslationUITestBase.php
index e7a7dfc9dd..9fc9f1167d 100644
--- a/core/modules/content_translation/src/Tests/ContentTranslationUITestBase.php
+++ b/core/modules/content_translation/src/Tests/ContentTranslationUITestBase.php
@@ -10,7 +10,7 @@
 use Drupal\Core\Url;
 use Drupal\language\Entity\ConfigurableLanguage;
 use Drupal\Component\Utility\SafeMarkup;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 
 /**
  * Tests the Content Translation UI.
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationUITestBase.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationUITestBase.php
index 370a6ed409..46c4d841c8 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationUITestBase.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationUITestBase.php
@@ -10,7 +10,7 @@
 use Drupal\Core\Url;
 use Drupal\language\Entity\ConfigurableLanguage;
 use Drupal\Component\Utility\SafeMarkup;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 
 /**
  * Tests the Content Translation UI.
diff --git a/core/modules/node/src/Tests/NodeBlockFunctionalTest.php b/core/modules/node/src/Tests/NodeBlockFunctionalTest.php
index 5a2e40a30d..0d94a04cb9 100644
--- a/core/modules/node/src/Tests/NodeBlockFunctionalTest.php
+++ b/core/modules/node/src/Tests/NodeBlockFunctionalTest.php
@@ -4,7 +4,7 @@
 
 use Drupal\block\Entity\Block;
 use Drupal\Core\EventSubscriber\MainContentViewSubscriber;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\user\RoleInterface;
 
 /**
diff --git a/core/modules/page_cache/src/Tests/PageCacheTagsIntegrationTest.php b/core/modules/page_cache/src/Tests/PageCacheTagsIntegrationTest.php
index 6ec8a29cf6..be704d16ed 100644
--- a/core/modules/page_cache/src/Tests/PageCacheTagsIntegrationTest.php
+++ b/core/modules/page_cache/src/Tests/PageCacheTagsIntegrationTest.php
@@ -5,8 +5,8 @@
 use Drupal\Core\EventSubscriber\MainContentViewSubscriber;
 use Drupal\Core\Language\LanguageInterface;
 use Drupal\simpletest\WebTestBase;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\node\NodeInterface;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 
 /**
  * Enables the page cache and tests its cache tags in various scenarios.
diff --git a/core/modules/rest/src/Tests/Views/StyleSerializerTest.php b/core/modules/rest/src/Tests/Views/StyleSerializerTest.php
index 83a154848e..b77c201303 100644
--- a/core/modules/rest/src/Tests/Views/StyleSerializerTest.php
+++ b/core/modules/rest/src/Tests/Views/StyleSerializerTest.php
@@ -9,7 +9,7 @@
 use Drupal\field\Entity\FieldConfig;
 use Drupal\field\Entity\FieldStorageConfig;
 use Drupal\language\Entity\ConfigurableLanguage;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\views\Entity\View;
 use Drupal\views\Plugin\views\display\DisplayPluginBase;
 use Drupal\views\Views;
diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index 2491bc84b3..c1046c71a5 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -18,7 +18,7 @@
 use Drupal\Core\Test\AssertMailTrait;
 use Drupal\Core\Test\FunctionalTestSetupTrait;
 use Drupal\Core\Url;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\Tests\Traits\Core\CronRunTrait;
 use Drupal\Tests\TestFileCreationTrait;
 use Drupal\Tests\XdebugRequestTrait;
diff --git a/core/modules/statistics/src/Tests/StatisticsReportsTest.php b/core/modules/statistics/src/Tests/StatisticsReportsTest.php
index ea597f40bb..b7181281be 100644
--- a/core/modules/statistics/src/Tests/StatisticsReportsTest.php
+++ b/core/modules/statistics/src/Tests/StatisticsReportsTest.php
@@ -3,7 +3,7 @@
 namespace Drupal\statistics\Tests;
 
 use Drupal\Core\Cache\Cache;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 
 /**
  * Tests display of statistics report blocks.
diff --git a/core/modules/system/src/Tests/System/TokenReplaceWebTest.php b/core/modules/system/src/Tests/System/TokenReplaceWebTest.php
index 21fe23ac19..957fb6977b 100644
--- a/core/modules/system/src/Tests/System/TokenReplaceWebTest.php
+++ b/core/modules/system/src/Tests/System/TokenReplaceWebTest.php
@@ -4,7 +4,7 @@
 
 use Drupal\Core\EventSubscriber\MainContentViewSubscriber;
 use Drupal\simpletest\WebTestBase;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 
 /**
  * Tests the token system integration.
diff --git a/core/modules/system/src/Tests/Cache/AssertPageCacheContextsAndTagsTrait.php b/core/modules/system/tests/src/Functional/Cache/AssertPageCacheContextsAndTagsTrait.php
similarity index 98%
rename from core/modules/system/src/Tests/Cache/AssertPageCacheContextsAndTagsTrait.php
rename to core/modules/system/tests/src/Functional/Cache/AssertPageCacheContextsAndTagsTrait.php
index 6bea791e91..667aacb256 100644
--- a/core/modules/system/src/Tests/Cache/AssertPageCacheContextsAndTagsTrait.php
+++ b/core/modules/system/tests/src/Functional/Cache/AssertPageCacheContextsAndTagsTrait.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\system\Tests\Cache;
+namespace Drupal\Tests\system\Functional\Cache;
 
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Url;
@@ -8,7 +8,7 @@
 /**
  * Provides test assertions for testing page-level cache contexts & tags.
  *
- * Can be used by test classes that extend \Drupal\simpletest\WebTestBase.
+ * Can be used by test classes that extend \Drupal\Tests\BrowserTestBase.
  */
 trait AssertPageCacheContextsAndTagsTrait {
 
diff --git a/core/modules/system/src/Tests/Cache/SessionExistsCacheContextTest.php b/core/modules/system/tests/src/Functional/Cache/SessionExistsCacheContextTest.php
similarity index 93%
rename from core/modules/system/src/Tests/Cache/SessionExistsCacheContextTest.php
rename to core/modules/system/tests/src/Functional/Cache/SessionExistsCacheContextTest.php
index 8815bf340f..2f84b4ede1 100644
--- a/core/modules/system/src/Tests/Cache/SessionExistsCacheContextTest.php
+++ b/core/modules/system/tests/src/Functional/Cache/SessionExistsCacheContextTest.php
@@ -1,16 +1,16 @@
 <?php
 
-namespace Drupal\system\Tests\Cache;
+namespace Drupal\Tests\system\Functional\Cache;
 
 use Drupal\Core\Url;
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Tests the 'session.exists' cache context service.
  *
  * @group Cache
  */
-class SessionExistsCacheContextTest extends WebTestBase {
+class SessionExistsCacheContextTest extends BrowserTestBase {
 
   /**
    * Modules to enable.
diff --git a/core/modules/toolbar/src/Tests/ToolbarCacheContextsTest.php b/core/modules/toolbar/src/Tests/ToolbarCacheContextsTest.php
index 6995d5985c..2ce5c1a382 100644
--- a/core/modules/toolbar/src/Tests/ToolbarCacheContextsTest.php
+++ b/core/modules/toolbar/src/Tests/ToolbarCacheContextsTest.php
@@ -5,7 +5,7 @@
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\EventSubscriber\MainContentViewSubscriber;
 use Drupal\simpletest\WebTestBase;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 
 
 /**
diff --git a/core/modules/tracker/tests/src/Functional/TrackerTest.php b/core/modules/tracker/tests/src/Functional/TrackerTest.php
index 17f95ee50d..aaa5a84f66 100644
--- a/core/modules/tracker/tests/src/Functional/TrackerTest.php
+++ b/core/modules/tracker/tests/src/Functional/TrackerTest.php
@@ -11,6 +11,7 @@
 use Drupal\node\Entity\Node;
 use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\Tests\BrowserTestBase;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 
 /**
  * Create and delete nodes and check for their display in the tracker listings.
diff --git a/core/modules/views/src/Tests/AssertViewsCacheTagsTrait.php b/core/modules/views/src/Tests/AssertViewsCacheTagsTrait.php
index 123a9cb5a2..b01e985450 100644
--- a/core/modules/views/src/Tests/AssertViewsCacheTagsTrait.php
+++ b/core/modules/views/src/Tests/AssertViewsCacheTagsTrait.php
@@ -3,7 +3,7 @@
 namespace Drupal\views\Tests;
 
 use Drupal\Core\Cache\Cache;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\views\Plugin\views\display\DisplayPluginBase;
 use Drupal\views\ViewExecutable;
 use Symfony\Component\HttpFoundation\Request;
diff --git a/core/modules/views/src/Tests/Handler/FieldWebTest.php b/core/modules/views/src/Tests/Handler/FieldWebTest.php
index 31de7be7e6..d5d0e380af 100644
--- a/core/modules/views/src/Tests/Handler/FieldWebTest.php
+++ b/core/modules/views/src/Tests/Handler/FieldWebTest.php
@@ -7,7 +7,7 @@
 use Drupal\Component\Utility\UrlHelper;
 use Drupal\Core\Render\RenderContext;
 use Drupal\Core\Url;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\views\Views;
 
 /**
diff --git a/core/modules/views/src/Tests/Plugin/CacheWebTest.php b/core/modules/views/src/Tests/Plugin/CacheWebTest.php
index 7786606376..8362b9ab3b 100644
--- a/core/modules/views/src/Tests/Plugin/CacheWebTest.php
+++ b/core/modules/views/src/Tests/Plugin/CacheWebTest.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\views\Tests\Plugin;
 
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\views\Plugin\views\display\DisplayPluginBase;
 use Drupal\views\Views;
 
diff --git a/core/modules/views/src/Tests/Plugin/ContextualFiltersBlockContextTest.php b/core/modules/views/src/Tests/Plugin/ContextualFiltersBlockContextTest.php
index 7fb70580a2..8ab5da190e 100644
--- a/core/modules/views/src/Tests/Plugin/ContextualFiltersBlockContextTest.php
+++ b/core/modules/views/src/Tests/Plugin/ContextualFiltersBlockContextTest.php
@@ -3,9 +3,9 @@
 namespace Drupal\views\Tests\Plugin;
 
 use Drupal\Core\Plugin\Context\ContextDefinitionInterface;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\views\Tests\ViewTestData;
 use Drupal\views\Tests\ViewTestBase;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
 
 /**
  * A test for contextual filters exposed as block context.
diff --git a/core/modules/views/src/Tests/Plugin/DisplayPageWebTest.php b/core/modules/views/src/Tests/Plugin/DisplayPageWebTest.php
index b5c853faec..8d9ad92de3 100644
--- a/core/modules/views/src/Tests/Plugin/DisplayPageWebTest.php
+++ b/core/modules/views/src/Tests/Plugin/DisplayPageWebTest.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\views\Tests\Plugin;
 
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\views\Views;
 
 /**
diff --git a/core/modules/views/src/Tests/Plugin/ExposedFormTest.php b/core/modules/views/src/Tests/Plugin/ExposedFormTest.php
index cfb3c0a071..c3733e2250 100644
--- a/core/modules/views/src/Tests/Plugin/ExposedFormTest.php
+++ b/core/modules/views/src/Tests/Plugin/ExposedFormTest.php
@@ -4,7 +4,7 @@
 
 use Drupal\Component\Utility\Html;
 use Drupal\entity_test\Entity\EntityTest;
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\views\Tests\ViewTestBase;
 use Drupal\views\ViewExecutable;
 use Drupal\views\Views;
diff --git a/core/modules/views/src/Tests/Plugin/PagerTest.php b/core/modules/views/src/Tests/Plugin/PagerTest.php
index 6ba4c069b4..b1e625949a 100644
--- a/core/modules/views/src/Tests/Plugin/PagerTest.php
+++ b/core/modules/views/src/Tests/Plugin/PagerTest.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\views\Tests\Plugin;
 
-use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\views\Views;
 use Drupal\language\Entity\ConfigurableLanguage;