Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in /opt/lampp/htdocs/forum/flarum/vendor/league/oauth1-client/tests/XingServerTest.php:12 Stack trace: #0 {main} thrown in /opt/lampp/htdocs/forum/flarum/vendor/league/oauth1-client/tests/XingServerTest.php on line 12