Fatal error: Uncaught Error: Class 'PHPUnit\Framework\Constraint\Constraint' not found in C:\xampp\htdocs\plugins\Symfony\Component\Notifier\Test\Constraint\NotificationIsQueued.php:20 Stack trace: #0 {main} thrown in C:\xampp\htdocs\plugins\Symfony\Component\Notifier\Test\Constraint\NotificationIsQueued.php on line 20