Anything that can fire an HTTP request and can be run in automation.
I usually run a selenium+behat setup that is completely unaware of the application implementation (separate autoloader, almost separate project, certainly separate/independent Docker container).
I’m testing my Mezzio apps with Codeception for e2e testing, and I have to say it feels cumbersome for something I’ve always done easily with zend-test.
Marc Guyer wrote a brief post on how to e2e testing on Mezzio with bare PHPUnit: https://marc.guyer.me/posts/mezzio-example/functional-testing/
Integrating it with packages like phpunit-dom-assertions would result in easier test-suite maintenance in my experience. @ocramius would you consider accepting such a package under mainstream Mezzio umbrella?
Ping @matthew