diff -u b/core/modules/toolbar/tests/src/FunctionalJavascript/ToolbarAdminMenuTest.php b/core/modules/toolbar/tests/src/Functional/ToolbarAdminMenuTest.php
--- b/core/modules/toolbar/tests/src/FunctionalJavascript/ToolbarAdminMenuTest.php
+++ b/core/modules/toolbar/tests/src/Functional/ToolbarAdminMenuTest.php
@@ -1,12 +1,12 @@
 <?php
 
-namespace Drupal\Tests\toolbar\FunctionalJavascript;
+namespace Drupal\Tests\toolbar\Functional;
 
 use Drupal\Core\EventSubscriber\MainContentViewSubscriber;
 use Drupal\Core\Language\LanguageInterface;
 use Drupal\Core\Url;
-use Drupal\FunctionalJavascriptTests\JavascriptTestBase;
 use Drupal\language\Entity\ConfigurableLanguage;
+use Drupal\Tests\BrowserTestBase;
 use Drupal\user\RoleInterface;
 
 /**
@@ -26,7 +26,7 @@
  *
  * @group toolbar
  */
-class ToolbarAdminMenuTest extends JavascriptTestBase {
+class ToolbarAdminMenuTest extends BrowserTestBase {
 
   /**
    * A user with permission to access the administrative toolbar.
@@ -331,9 +331,8 @@
     // Request a new page to refresh the drupalSettings object.
     $subtrees_hash = $this->getSubtreesHash();
 
-    $this->drupalGet('toolbar/subtrees/' . $subtrees_hash, ['query' => [MainContentViewSubscriber::WRAPPER_FORMAT => 'drupal_ajax']]);
-    $ajax_result = json_decode($this->xpath('//textarea')[0]->getValue(), TRUE);
-    $this->assertResponse('200');
+    $this->drupalGet('toolbar/subtrees/' . $subtrees_hash, ['query' => [MainContentViewSubscriber::WRAPPER_FORMAT => 'drupal_ajax']], ['X-Requested-With: XMLHttpRequest']);
+    $ajax_result = json_decode($this->getSession()->getPage()->getContent(), TRUE);
     $this->assertEqual($ajax_result[0]['command'], 'setToolbarSubtrees', 'Subtrees response uses the correct command.');
     $this->assertEqual(array_keys($ajax_result[0]['subtrees']), ['system-admin_content', 'system-admin_structure', 'system-themes_page', 'system-modules_list', 'system-admin_config', 'entity-user-collection', 'front'], 'Correct subtrees returned.');
   }