tldr; First of all I would like to explain why: In my opinion sometimes you can write some of your E2E tests and your User-acceptance tests in one go, together. I'm not saying all of them, some E2E tests can cover exceptional cases and often are on the sad path in terms of UAT. Both of them are rather flaky in terms of feedback and can't give any detailed hint where the test failed, except the approximate region of your application. Both hit the application in the running state, so why not write...