Writing Great Unit Tests: Best and Worst Practices by Steve Sanderson
This blog post is aimed at developers with at least a small amount of unit testing experience. If you've never written a unit test, please read an introduction and have a go at it first.
What's the difference between a good unit test and a bad one? How do you learn how to write good unit tests? It's far from obvious. Even if you're a brilliant coder with decades of experience, your existing knowledge and habits won't automatically lead you to write good unit tests, because it's a different kind of coding and most people start with unhelpful false assumptions about what unit tests are supposed to achieve.
Most of the unit tests I see are pretty unhelpful. I'm not blaming the developer: Usually, he or she just got told to start unit testing, so they installed NUnit