diff --git a/core/tests/Drupal/Tests/Core/Ajax/AjaxCommandsTest.php b/core/tests/Drupal/Tests/Core/Ajax/AjaxCommandsTest.php
index 4db1d02..1dd66b8 100644
--- a/core/tests/Drupal/Tests/Core/Ajax/AjaxCommandsTest.php
+++ b/core/tests/Drupal/Tests/Core/Ajax/AjaxCommandsTest.php
@@ -25,6 +25,7 @@
 use Drupal\Core\Ajax\SetDialogTitleCommand;
 use Drupal\Core\Ajax\RedirectCommand;
 use Drupal\Core\Ajax\UpdateBuildIdCommand;
+use Drupal\Core\Ajax\OpenDialogCommand;
 
 /**
  * Test coverage for various classes in the \Drupal\Core\Ajax namespace.
@@ -293,27 +294,16 @@ public function testSettingsCommand() {
    * @covers \Drupal\Core\Ajax\OpenDialogCommand
    */
   public function testOpenDialogCommand() {
-    $command = $this->getMockBuilder('Drupal\Core\Ajax\OpenDialogCommand')
-      ->setConstructorArgs([
-        '#some-dialog', 'Title', '<p>Text!</p>', [
-          'url' => FALSE,
-          'width' => 500,
-        ],
-      ])
-      ->setMethods(['getRenderedContent'])
-      ->getMock();
-
-    // This method calls the render service, which isn't available. We want it
-    // to do nothing so we mock it to return a known value.
-    $command->expects($this->once())
-      ->method('getRenderedContent')
-      ->willReturn('rendered content');
+    $command = new OpenDialogCommand('#some-dialog', 'Title', '<p>Text!</p>', [
+      'url' => FALSE,
+      'width' => 500,
+    ]);
 
     $expected = [
       'command' => 'openDialog',
       'selector' => '#some-dialog',
       'settings' => NULL,
-      'data' => 'rendered content',
+      'data' => '<p>Text!</p>',
       'dialogOptions' => [
         'url' => FALSE,
         'width' => 500,
@@ -322,6 +312,10 @@ public function testOpenDialogCommand() {
       ],
     ];
     $this->assertEquals($expected, $command->render());
+
+    $command->setDialogTitle('New title');
+    $expected['dialogOptions']['title'] = 'New title';
+    $this->assertEquals($expected, $command->render());
   }
 
   /**