Fatal error: Uncaught Error: Class 'Drupal\Tests\BrowserTestBase' not found in /var/www/html/tmp/contrib/flag/modules/flag_follower/tests/src/Functional/FlagFollowerUITest.php:11 Stack trace: #0 {main} thrown in /var/www/html/tmp/contrib/flag/modules/flag_follower/tests/src/Functional/FlagFollowerUITest.php on line 11