I always thought that if I ran composer install --no-dev that test modules in the Dev directory would not be populated but after finding a payment with that processed with “fake payment method”, I found out that is not true.
These test modules are found in dev/tests/integration/_files/Magento/ and are generated from vendor/magento/magento2-base/dev/. I can just disable them but is that the proper method? I know how to stop the payment issue I mentioned but is there something I am supposed to do to stop the test modules from generating in the dev directory in the first place?