diff --git a/core/modules/image/src/Tests/ImageFieldDisplayTest.php b/core/modules/image/src/Tests/ImageFieldDisplayTest.php
index fc6854b6f2ef5a54abe363e6f1d0de4ecc84e9ed..f0b04cbfdef87dae7b7f2c86425a4307eaec70ad 100644
--- a/core/modules/image/src/Tests/ImageFieldDisplayTest.php
+++ b/core/modules/image/src/Tests/ImageFieldDisplayTest.php
@@ -58,7 +58,7 @@ function _testImageFieldFormatters($scheme) {
     $this->assertLinkByHref(\Drupal::url('image.style_list'), 0, 'Link to image styles configuration is found');
 
     // Remove 'administer image styles' permission from testing admin user.
-    $admin_user_roles = $this->admin_user->getRoles(TRUE);
+    $admin_user_roles = $this->adminUser->getRoles(TRUE);
     user_role_change_permissions(reset($admin_user_roles), array('administer image styles' => FALSE));
 
     // Go to manage display page again.
@@ -127,7 +127,7 @@ function _testImageFieldFormatters($scheme) {
       $this->assertResponse('403', 'Access denied to original image as anonymous user.');
 
       // Log in again.
-      $this->drupalLogin($this->admin_user);
+      $this->drupalLogin($this->adminUser);
     }
 
     // Test the image linked to content formatter.
diff --git a/core/modules/image/src/Tests/ImageFieldTestBase.php b/core/modules/image/src/Tests/ImageFieldTestBase.php
index 2b8a648fc2dc2c497155ec54f2d9c8fcdd10e48c..d8bee126dc58eacb30340cd847dfb7ffc3d68d18 100644
--- a/core/modules/image/src/Tests/ImageFieldTestBase.php
+++ b/core/modules/image/src/Tests/ImageFieldTestBase.php
@@ -34,7 +34,12 @@ abstract class ImageFieldTestBase extends WebTestBase {
    */
   public static $modules = array('node', 'image', 'field_ui', 'image_module_test');
 
-  protected $admin_user;
+  /**
+   * An user with permissions to administer content types and image styles.
+   *
+   * @var \Drupal\user\UserInterface
+   */
+  protected $adminUser;
 
   protected function setUp() {
     parent::setUp();
@@ -45,8 +50,8 @@ protected function setUp() {
       $this->drupalCreateContentType(array('type' => 'article', 'name' => 'Article'));
     }
 
-    $this->admin_user = $this->drupalCreateUser(array('access content', 'access administration pages', 'administer site configuration', 'administer content types', 'administer node fields', 'administer nodes', 'create article content', 'edit any article content', 'delete any article content', 'administer image styles', 'administer node display'));
-    $this->drupalLogin($this->admin_user);
+    $this->adminUser = $this->drupalCreateUser(array('access content', 'access administration pages', 'administer site configuration', 'administer content types', 'administer node fields', 'administer nodes', 'create article content', 'edit any article content', 'delete any article content', 'administer image styles', 'administer node display'));
+    $this->drupalLogin($this->adminUser);
   }
 
   /**
diff --git a/core/modules/responsive_image/src/Tests/ResponsiveImageFieldDisplayTest.php b/core/modules/responsive_image/src/Tests/ResponsiveImageFieldDisplayTest.php
index 09efc576b1e779c1750d5b288fab1071998a6979..b09a9e5f87e809cf92a631671e48cc7ff058c174 100644
--- a/core/modules/responsive_image/src/Tests/ResponsiveImageFieldDisplayTest.php
+++ b/core/modules/responsive_image/src/Tests/ResponsiveImageFieldDisplayTest.php
@@ -40,7 +40,7 @@ protected function setUp() {
     parent::setUp();
 
     // Create user.
-    $this->admin_user = $this->drupalCreateUser(array(
+    $this->adminUser = $this->drupalCreateUser(array(
       'administer responsive images',
       'access content',
       'access administration pages',
@@ -53,7 +53,7 @@ protected function setUp() {
       'delete any article content',
       'administer image styles'
     ));
-    $this->drupalLogin($this->admin_user);
+    $this->drupalLogin($this->adminUser);
     // Add responsive image mapping.
     $this->responsiveImgMapping = entity_create('responsive_image_mapping', array(
       'id' => 'mapping_one',
@@ -180,7 +180,7 @@ protected function doTestResponsiveImageFieldFormatters($scheme, $empty_styles =
       $this->assertResponse('403', 'Access denied to original image as anonymous user.');
 
       // Log in again.
-      $this->drupalLogin($this->admin_user);
+      $this->drupalLogin($this->adminUser);
     }
 
     // Use the responsive image formatter with a responsive image mapping.