In this post I will try to accumulate different info on game (preferrably automated) testing. I will add generic articles on a subject, and specifically on testing in XNA, but not for other freameworks/languages.
Automated game testing is particularly difficult to implement, yet games are usually very hard to test fully. So even partial core testing is helpful.
First will be two topics on Game Development StackExchange. Unit Testing a C#/XNA Game Project and How common is automated testing in game development?. They also contain a handful number of link to some more articles on this subject.
As always you are welcome to add your finding on a subject in comments, so I can extend and improve the list.