Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in C:\xampp\htdocs\adminlte3\vendor\sendgrid\php-http-client\test\unit\FilesExistTest.php:7 Stack trace: #0 {main} thrown in C:\xampp\htdocs\adminlte3\vendor\sendgrid\php-http-client\test\unit\FilesExistTest.php on line 7