Have you ever been in an interview that got awkward because the candidate kept getting stuck?
It happens all the time: a programmer is given an interview problem and an hour to solve it over the phone in a plain text editor or on a whiteboard. They take a crack at it and write a totally reasonable solution.
There’s just one hangup: the candidate hasn’t found that weird bug in their solution. If they could just run their code, it'd be super obvious. But they can't.