Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in C:\xampp\htdocs\addfirst\vendor\mercadopago\dx-php\tests\SDKTest.php:12 Stack trace: #0 {main} thrown in C:\xampp\htdocs\addfirst\vendor\mercadopago\dx-php\tests\SDKTest.php on line 12