PHPUnit Test small part of your code You write a lot of these. Pretty fast For Modules, Plugins and/or any seperate - Test results of PHP functions/classes Primarily for your services. Functional From perspective of user Tests more generally functionality Simulates a web request Write less of these Slower For Modules, Plugins, Sites and/or any controller or twig template. Your twig templates. Only for testing Controllers. 9 All testing is done with Codeception ❤