One of the most troubling parts of unit testing, to me, is keeping things organized. For the past year, I've been managing my tests like this:
Tests for large classes would get out of control! There could be several test methods for a single method on the original class. Imagine a tester class if the original class had 20 methods.
However, thanks to this excellent tip from Phil Haack, this situation can be cleaned up and put into an easier to manage form.
By structuring your unit test classes to contain nested classes, each designated to test a single function, you can have a set of tests look like this: