Fatal error: Uncaught Error: Class "Drupal\Tests\system\Functional\Cache\PageCacheTagsTestBase" not found in /home/www/drupal8/test/core/modules/user/tests/src/Functional/UserPasswordResetTest.php:16 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/user/tests/src/Functional/UserPasswordResetTest.php on line 16