In fact, one of the most useful times to write tests is before I start programming. When I need to add a feature, I begin by writing the test. This isn’t as backward as it sounds. By writing the test, I’m asking myself what needs to be done to add the function. Writing the test also concentrates me on the interface rather than the implementation (always a good thing). It also means I have a clear point at which I’m done coding—when the test works.
