Fatal error: Uncaught Error: Class 'PHPUnit\Framework\TestCase' not found in D:\xampp\htdocs\psp\backend\vendor\laravel\framework\src\Illuminate\Foundation\Testing\TestCase.php:18 Stack trace: #0 {main} thrown in D:\xampp\htdocs\psp\backend\vendor\laravel\framework\src\Illuminate\Foundation\Testing\TestCase.php on line 18