Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in C:\xampp\htdocs\r10csm\vendor\symfony\mime\Tests\HtmlToTextConverter\DefaultHtmlToTextConverterTest.php:17 Stack trace: #0 {main} thrown in C:\xampp\htdocs\r10csm\vendor\symfony\mime\Tests\HtmlToTextConverter\DefaultHtmlToTextConverterTest.php on line 17