Unit Testing and the GAC
Note to self: If you make changes to an assembly that is in the GAC, make sure you uninstall it from the GAC before running your unit tests. I was doing some refactoring and changed the signatures of a couple of methods. Recompiled and ran my nUnit unit tests and was getting a very odd "System.MissingMethodException". I was baffled until I recalled that the old version of this assembly was still in the GAC so that's what my unit tests were running.