diff --git a/core/lib/Drupal/Core/EventSubscriber/DefaultExceptionSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/DefaultExceptionSubscriber.php
index 93d7471..f4b4506 100644
--- a/core/lib/Drupal/Core/EventSubscriber/DefaultExceptionSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/DefaultExceptionSubscriber.php
@@ -174,7 +174,7 @@ protected function onJson(GetResponseForExceptionEvent $event) {
     // of message to be displayed,
     $data = [];
     if (error_displayable($error) && $message = $exception->getMessage()) {
-      $data = [$message];
+      $data = [sprintf('A fatal error occurred: %s', $message)];
     }
 
     $response = new JsonResponse($data, Response::HTTP_INTERNAL_SERVER_ERROR);
diff --git a/core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php
index 7befb00..5f13978 100644
--- a/core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php
@@ -39,7 +39,7 @@ protected static function getPriority() {
    *   The event to process.
    */
   public function on403(GetResponseForExceptionEvent $event) {
-    $response = new JsonResponse(NULL, Response::HTTP_FORBIDDEN);
+    $response = new JsonResponse([], Response::HTTP_FORBIDDEN);
     $event->setResponse($response);
   }
 
@@ -50,7 +50,7 @@ public function on403(GetResponseForExceptionEvent $event) {
    *   The event to process.
    */
   public function on404(GetResponseForExceptionEvent $event) {
-    $response = new JsonResponse(NULL, Response::HTTP_NOT_FOUND);
+    $response = new JsonResponse([], Response::HTTP_NOT_FOUND);
     $event->setResponse($response);
   }
 
@@ -61,7 +61,7 @@ public function on404(GetResponseForExceptionEvent $event) {
    *   The event to process.
    */
   public function on405(GetResponseForExceptionEvent $event) {
-    $response = new JsonResponse(NULL, Response::HTTP_METHOD_NOT_ALLOWED);
+    $response = new JsonResponse([], Response::HTTP_METHOD_NOT_ALLOWED);
     $event->setResponse($response);
   }
 
diff --git a/core/modules/quickedit/src/Tests/QuickEditLoadingTest.php b/core/modules/quickedit/src/Tests/QuickEditLoadingTest.php
index 3de74b1..afdb728 100644
--- a/core/modules/quickedit/src/Tests/QuickEditLoadingTest.php
+++ b/core/modules/quickedit/src/Tests/QuickEditLoadingTest.php
@@ -84,7 +84,7 @@ public function testUserWithoutPermission() {
     // Retrieving the metadata should result in an empty 403 response.
     $post = array('fields[0]' => 'node/1/body/en/full');
     $response = $this->drupalPost('quickedit/metadata', 'application/json', $post);
-    $this->assertIdentical('{}', $response);
+    $this->assertIdentical('[]', $response);
     $this->assertResponse(403);
 
     // Quick Edit's JavaScript would SearchRankingTestnever hit these endpoints if the metadata
@@ -261,7 +261,6 @@ public function testUserWithPermission() {
       );
       $post += $edit + $this->getAjaxPageStatePostData();
       $response = $this->drupalPost('quickedit/form/' . 'node/1/body/en/full', 'application/vnd.drupal-ajax', $post);
-      $this->assertIdentical('[]', $response);
       $this->assertResponse(200);
       $ajax_commands = Json::decode($response);
       $this->assertIdentical(1, count($ajax_commands), 'The field form HTTP request results in one AJAX command.');
@@ -271,8 +270,11 @@ public function testUserWithPermission() {
       // Save the entity.
       $post = array('nocssjs' => 'true');
       $response = $this->drupalPost('quickedit/entity/' . 'node/1', 'application/json', $post);
-      $this->assertIdentical('[]', $response);
       $this->assertResponse(200);
+      $ajax_commands = Json::decode($response);
+      $this->assertIdentical(1, count($ajax_commands));
+      $this->assertIdentical('quickeditEntitySaved', $ajax_commands[0]['command'], 'The first AJAX command is an quickeditEntitySaved command.');
+      $this->assertEqual($ajax_commands[0]['data'], ['entity_type' => 'node', 'entity_id' => 1], 'Updated entity type and ID returned');
 
       // Test that a revision was created with the correct log message.
       $vids = \Drupal::entityManager()->getStorage('node')->revisionIds(node_load(1));
diff --git a/core/modules/rest/src/Tests/AuthTest.php b/core/modules/rest/src/Tests/AuthTest.php
index b53beaf..dd8b3f4 100644
--- a/core/modules/rest/src/Tests/AuthTest.php
+++ b/core/modules/rest/src/Tests/AuthTest.php
@@ -39,7 +39,7 @@ public function testRead() {
     // Try to read the resource as an anonymous user, which should not work.
     $this->httpRequest($entity->getSystemPath(), 'GET', NULL, $this->defaultMimeType);
     $this->assertResponse('401', 'HTTP response code is 401 when the request is not authenticated and the user is anonymous.');
-    $this->assertText('A fatal error occurred: No authentication credentials provided.');
+    $this->assertRaw(json_encode(['A fatal error occurred: No authentication credentials provided.']));
 
     // Ensure that cURL settings/headers aren't carried over to next request.
     unset($this->curlHandle);