diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTestBase.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTestBase.php
deleted file mode 100644
index 4d7750945a..0000000000
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTestBase.php
+++ /dev/null
@@ -1,23 +0,0 @@
-<?php
-
-namespace Drupal\FunctionalJavascriptTests\Ajax;
-
-use Drupal\FunctionalJavascriptTests\DrupalSelenium2Driver;
-use Drupal\FunctionalJavascriptTests\JavascriptTestBase;
-
-/**
- * Provides a base class for Ajax tests.
- */
-abstract class AjaxTestBase extends JavascriptTestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  public static $modules = ['node', 'ajax_test', 'ajax_forms_test'];
-
-  /**
-   * {@inheritdoc}
-   */
-  protected $minkDefaultDriverClass = DrupalSelenium2Driver::class;
-
-}
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/CommandsTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/CommandsTest.php
index 74b3e09d4e..3e3d684fe1 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/CommandsTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/CommandsTest.php
@@ -2,12 +2,26 @@
 
 namespace Drupal\FunctionalJavascriptTests\Ajax;
 
+use Drupal\FunctionalJavascriptTests\DrupalSelenium2Driver;
+use Drupal\FunctionalJavascriptTests\JavascriptTestBase;
+
 /**
  * Performs tests on AJAX framework commands.
  *
  * @group Ajax
  */
-class CommandsTest extends AjaxTestBase {
+class CommandsTest extends JavascriptTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['node', 'ajax_test', 'ajax_forms_test'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $minkDefaultDriverClass = DrupalSelenium2Driver::class;
+
   /**
    * Tests the various Ajax Commands.
    */
@@ -31,6 +45,16 @@ public function testAjaxCommands() {
       return $element && $element->getHtml() === 'This will be placed after';
     }));
 
+    // Tests the 'alert' command.
+    $test_alert_command = <<<JS
+window.alert = function() {
+  document.body.innerHTML += '<div class="alert-command">Alert</div>';
+};
+JS;
+    $session->executeScript($test_alert_command);
+    $page->pressButton("AJAX 'Alert': Click to alert");
+    $this->assertWaitPageContains('<div class="alert-command">Alert</div>');
+
     // Tests the 'append' command.
     $page->pressButton("AJAX 'Append': Click to append something");
     $this->assertWaitPageContains('<div id="append_div">Append inside this div<div>Appended text</div></div>');
@@ -95,7 +119,7 @@ public function testAjaxCommands() {
 };
 JS;
     $session->executeScript($test_settings_command);
-    // 'Click' not works, need 'mousedown'. See more in misc/ajax.es6.js.
+    // @todo: Replace after https://www.drupal.org/project/drupal/issues/2616184
     $session->executeScript('window.jQuery("#edit-settings-command-example").mousedown();');
     $this->assertWaitPageContains('<div class="test-settings-command">42</div>');
   }
diff --git a/core/tests/Drupal/KernelTests/Core/Ajax/AjaxTestBase.php b/core/tests/Drupal/KernelTests/Core/Ajax/AjaxTestBase.php
deleted file mode 100644
index f12bfaad66..0000000000
--- a/core/tests/Drupal/KernelTests/Core/Ajax/AjaxTestBase.php
+++ /dev/null
@@ -1,61 +0,0 @@
-<?php
-
-namespace Drupal\KernelTests\Core\Ajax;
-
-use Drupal\KernelTests\KernelTestBase;
-
-/**
- * Provides a base class for Ajax tests.
- */
-abstract class AjaxTestBase extends KernelTestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  public static $modules = ['system', 'node', 'ajax_test', 'ajax_forms_test'];
-
-  /**
-   * Asserts the array of Ajax commands contains the searched command.
-   *
-   * An AjaxResponse object stores an array of Ajax commands. This array
-   * sometimes includes commands automatically provided by the framework in
-   * addition to commands returned by a particular controller. During testing,
-   * we're usually interested that a particular command is present, and don't
-   * care whether other commands precede or follow the one we're interested in.
-   * Additionally, the command we're interested in may include additional data
-   * that we're not interested in. Therefore, this function simply asserts that
-   * one of the commands in $haystack contains all of the keys and values in
-   * $needle. Furthermore, if $needle contains a 'settings' key with an array
-   * value, we simply assert that all keys and values within that array are
-   * present in the command we're checking, and do not consider it a failure if
-   * the actual command contains additional settings that aren't part of
-   * $needle.
-   *
-   * @param $haystack
-   *   An array of rendered Ajax commands returned by the server.
-   * @param $needle
-   *   Array of info we're expecting in one of those commands.
-   * @param $message
-   *   An assertion message.
-   */
-  protected function assertCommand($haystack, $needle, $message) {
-    $found = FALSE;
-    foreach ($haystack as $command) {
-      // If the command has additional settings that we're not testing for, do
-      // not consider that a failure.
-      if (isset($command['settings']) && is_array($command['settings']) && isset($needle['settings']) && is_array($needle['settings'])) {
-        $command['settings'] = array_intersect_key($command['settings'], $needle['settings']);
-      }
-      // If the command has additional data that we're not testing for, do not
-      // consider that a failure. Also, == instead of ===, because we don't
-      // require the key/value pairs to be in any particular order
-      // (http://php.net/manual/language.operators.array.php).
-      if (array_intersect_key($command, $needle) == $needle) {
-        $found = TRUE;
-        break;
-      }
-    }
-    $this->assertTrue($found, $message);
-  }
-
-}
diff --git a/core/tests/Drupal/KernelTests/Core/Ajax/CommandsTest.php b/core/tests/Drupal/KernelTests/Core/Ajax/CommandsTest.php
index 2747a9f834..a6bbe0b270 100644
--- a/core/tests/Drupal/KernelTests/Core/Ajax/CommandsTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Ajax/CommandsTest.php
@@ -4,6 +4,7 @@
 
 use Drupal\Core\Ajax\AjaxResponse;
 use Drupal\Core\EventSubscriber\AjaxResponseSubscriber;
+use Drupal\KernelTests\KernelTestBase;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
 use Symfony\Component\HttpKernel\HttpKernelInterface;
@@ -13,7 +14,12 @@
  *
  * @group Ajax
  */
-class CommandsTest extends AjaxTestBase {
+class CommandsTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['system', 'node', 'ajax_test', 'ajax_forms_test'];
 
   /**
    * {@inheritdoc}
@@ -58,4 +64,48 @@ public function testAttachedSettings() {
     $assert('Settings command exists when JS aggregation is enabled.');
   }
 
+  /**
+   * Asserts the array of Ajax commands contains the searched command.
+   *
+   * An AjaxResponse object stores an array of Ajax commands. This array
+   * sometimes includes commands automatically provided by the framework in
+   * addition to commands returned by a particular controller. During testing,
+   * we're usually interested that a particular command is present, and don't
+   * care whether other commands precede or follow the one we're interested in.
+   * Additionally, the command we're interested in may include additional data
+   * that we're not interested in. Therefore, this function simply asserts that
+   * one of the commands in $haystack contains all of the keys and values in
+   * $needle. Furthermore, if $needle contains a 'settings' key with an array
+   * value, we simply assert that all keys and values within that array are
+   * present in the command we're checking, and do not consider it a failure if
+   * the actual command contains additional settings that aren't part of
+   * $needle.
+   *
+   * @param $haystack
+   *   An array of rendered Ajax commands returned by the server.
+   * @param $needle
+   *   Array of info we're expecting in one of those commands.
+   * @param $message
+   *   An assertion message.
+   */
+  protected function assertCommand($haystack, $needle, $message) {
+    $found = FALSE;
+    foreach ($haystack as $command) {
+      // If the command has additional settings that we're not testing for, do
+      // not consider that a failure.
+      if (isset($command['settings']) && is_array($command['settings']) && isset($needle['settings']) && is_array($needle['settings'])) {
+        $command['settings'] = array_intersect_key($command['settings'], $needle['settings']);
+      }
+      // If the command has additional data that we're not testing for, do not
+      // consider that a failure. Also, == instead of ===, because we don't
+      // require the key/value pairs to be in any particular order
+      // (http://php.net/manual/language.operators.array.php).
+      if (array_intersect_key($command, $needle) == $needle) {
+        $found = TRUE;
+        break;
+      }
+    }
+    $this->assertTrue($found, $message);
+  }
+
 }