diff -u b/core/modules/user/tests/src/Functional/UserPermissionsTest.php b/core/modules/user/tests/src/Functional/UserPermissionsTest.php
--- b/core/modules/user/tests/src/Functional/UserPermissionsTest.php
+++ b/core/modules/user/tests/src/Functional/UserPermissionsTest.php
@@ -175,14 +175,14 @@
     // to 'access site reports'.
     $this->drupalGet('admin/people/permissions');
     $next_row = $this->xpath('//tr[@data-drupal-selector=\'edit-permissions-access-content\']/following-sibling::tr[1]');
-    $this->assertEqual('edit-permissions-access-site-reports', $next_row[0]->attributes()['data-drupal-selector']);
+    $this->assertEqual('edit-permissions-access-site-reports', $next_row[0]->getAttribute('data-drupal-selector'));
 
     // When Node is installed the 'access content' permission is listed next to
     // to 'view own unpublished content'.
     \Drupal::service('module_installer')->install(['node']);
     $this->drupalGet('admin/people/permissions');
     $next_row = $this->xpath('//tr[@data-drupal-selector=\'edit-permissions-access-content\']/following-sibling::tr[1]');
-    $this->assertEqual('edit-permissions-view-own-unpublished-content', $next_row[0]->attributes()['data-drupal-selector']);
+    $this->assertEqual('edit-permissions-view-own-unpublished-content', $next_row[0]->getAttribute('data-drupal-selector'));
   }
 
 }