I've always thought that a good way to do a practical interview is to get the candidate to do a fizzbuzz. Then tell them that the requirements have changed, the

I've always thought that a good way to do a practical interview is to get the candidate to do a fizzbuzz. Then tell them that the requirements have changed, they need to add feature x. Then feature y, and so on. I reckon this would avoid ppl who just learn the test, and comes some way to emulating what actually happens in a real world job. But anyways, I'm not a hiring manager, so someone go out and try this and tell me why it's a terrible idea.