TestClasses的Symfony Reflection返回在vendor / symfony / framework-bundle / Test / KernelTestCase.php中找不到的'PHPUnit \\ Framework \\ TestCase'

So, I'm trying to extract details via reflection from all Test classes in my Symfony Application.

When I run bin/phpunit, all tests pass. So, with this, I understand that phpunit is installed correctly, composer is set up correctly, etc..

So, when I want to create a class via Reflection, either with native PHP code or with Symfony's PropertyInfoExtractor, it throws this message:

[2019-07-27 08:30:50] php.CRITICAL: Fatal Error: Class 'PHPUnit\Framework\TestCase' not found {"exception":"[object] (Symfony\\Component\\Debug\\Exception\\FatalErrorException(code: 0): Error: Class 'PHPUnit\\Framework\\TestCase' not found at /Users/user/Documents/project/vendor/symfony/framework-bundle/Test/KernelTestCase.php:24)"} []

So, what is wrong with it?