Many programmers have a hard time writing good unit-tests for code that involves time. For example, how do you test time-outs, or periodic clean-up jobs? I have seen many tests that create elaborate set-ups with lots of dependencies, or introduce real time gaps, just to be able to test those parts. However, if you structure the code the right way, much of the complexity disappears. Here is an example of a technique that lets you test time-related code with ease.