Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in C:\xampp\htdocs\astra-backoffice\vendor\symfony\mime\Tests\Encoder\Rfc2231EncoderTest.php:17 Stack trace: #0 {main} thrown in C:\xampp\htdocs\astra-backoffice\vendor\symfony\mime\Tests\Encoder\Rfc2231EncoderTest.php on line 17