implemented a feature or because you forget on a certain in your test or the setup code is not correct now when you present this idea to a lot of people they always come up with this phrase I can't write a test first because I don't know what I'm going to build and this can mean different things it can mean that you don't understand what business is asking you to do right and in this case it's true you cannot write any test but you cannot write any production code either what you have to do is go back to business and ask for