Fatal error: Uncaught Error: Class "Drupal\Tests\BrowserTestBase" not found in /home/www/drupal8/test/core/modules/basic_auth/tests/src/Functional/BasicAuthTest.php:17 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/basic_auth/tests/src/Functional/BasicAuthTest.php on line 17