diff --git a/core/modules/help_topics/tests/src/Functional/HelpTopicTest.php b/core/modules/help_topics/tests/src/Functional/HelpTopicTest.php
index 769850a16e..2e54274174 100644
--- a/core/modules/help_topics/tests/src/Functional/HelpTopicTest.php
+++ b/core/modules/help_topics/tests/src/Functional/HelpTopicTest.php
@@ -3,6 +3,7 @@
 namespace Drupal\Tests\help_topics\Functional;
 
 use Drupal\Tests\BrowserTestBase;
+use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\Tests\system\Functional\Menu\AssertBreadcrumbTrait;
 
 /**
@@ -12,6 +13,7 @@
  */
 class HelpTopicTest extends BrowserTestBase {
   use AssertBreadcrumbTrait;
+  use AssertPageCacheContextsAndTagsTrait;
 
   /**
    * Modules to enable.
@@ -166,9 +168,7 @@ protected function verifyHelp($response = 200) {
         $name = $info['name'];
         $session->titleEquals($name . ' | Drupal');
         $session->responseContains('<h1 class="page-title">' . $name . '</h1>');
-        foreach ($info['tags'] as $tag) {
-          $session->responseHeaderContains('X-Drupal-Cache-Tags', $tag);
-        }
+        $this->assertCacheTags($info['tags']);
       }
     }
   }
diff --git a/core/modules/help_topics/tests/src/Unit/HelpTopicTwigLoaderTest.php b/core/modules/help_topics/tests/src/Unit/HelpTopicTwigLoaderTest.php
index f014c09499..cf4b8c61c8 100644
--- a/core/modules/help_topics/tests/src/Unit/HelpTopicTwigLoaderTest.php
+++ b/core/modules/help_topics/tests/src/Unit/HelpTopicTwigLoaderTest.php
@@ -26,7 +26,7 @@ class HelpTopicTwigLoaderTest extends UnitTestCase {
    *
    * @var array
    */
-  protected static $directories;
+  protected $directories;
 
   /**
    * {@inheritdoc}
@@ -47,8 +47,8 @@ public function testConstructor() {
     // and non-existent directories were omitted.
     $paths = $this->helpLoader->getPaths(HelpTopicTwigLoader::MAIN_NAMESPACE);
     $this->assertEquals(count($paths), 2);
-    $this->assertTrue(in_array(self::$directories['module']['test'] . '/help_topics', $paths));
-    $this->assertTrue(in_array(self::$directories['theme']['test'] . '/help_topics', $paths));
+    $this->assertTrue(in_array($this->directories['module']['test'] . '/help_topics', $paths));
+    $this->assertTrue(in_array($this->directories['theme']['test'] . '/help_topics', $paths));
   }
 
   /**
@@ -56,6 +56,9 @@ public function testConstructor() {
    *
    * @param string $type
    *   Type of handler to return: 'module' or 'theme'.
+   *
+   * @return \PHPUnit\Framework\MockObject\MockObject
+   *   The mock of module or theme handler.
    */
   protected function getHandlerMock($type) {
     if ($type == 'module') {
@@ -74,7 +77,7 @@ protected function getHandlerMock($type) {
 
     $handler
       ->method($method)
-      ->willReturn($this::$directories[$type]);
+      ->willReturn($this->directories[$type]);
 
     return $handler;
   }
@@ -99,7 +102,7 @@ protected function setUpVfs() {
       ],
     ]);
 
-    self::$directories = [
+    $this->directories = [
       'root' => vfsStream::url('root'),
       'module' => [
         'test' => vfsStream::url('root/modules/test'),