Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in /home/alkhalaffamily/public_html/felhal/vendor/sebastian/environment/tests/OperatingSystemTest.php:17 Stack trace: #0 {main} thrown in /home/alkhalaffamily/public_html/felhal/vendor/sebastian/environment/tests/OperatingSystemTest.php on line 17