One of the best things you could do in a whiteboard interview is just start writing effective unit test cases without being prompted into it. When I joined my

One of the best things you could do in a whiteboard interview is just start writing effective unit test cases without being prompted into it. When I joined my current company, it was still tiny and sketchy and I got shanghaied into a surprise full day interview by the promise of an informal two hour tour. A two hour tour... At one point I was given 1.5 hours to write an implementation of a very core library that most software engineers take for granted every day. Trying to have fun with it, I spent about 20 minutes writing a design document, about 30 minutes coding the implementation, and then the last 40 minutes writing a dozen or so unit test cases (as well as a simple standalone unit test framework). When I ran out of time, only maybe 2/3rds of my test cases passed, and I had just narrowed the problem down to a flaw in one of the assumptions I had enumerated in my design document. All the interviewers seemed pretty impressed by the documentation and test coverage, and didn't really care about the implementation, mostly because it was relatively boring by design.