This is what a great QA tester will do. Good devs don't ship code with known bugs - but they will miss things because they code to the feature/user story/known

This is what a great QA tester will do. Good devs don't ship code with known bugs - but they will miss things because they code to the feature/user story/known behavior. That's what their job is. A good QA person's job will be to spend a whole lot of time thinking about how to break the dev's app that the dev missed.