To me, there is a fundamental mistake when “interaction” is considered the main goal in videogame testing. Interaction and entertainment are key factors, but the focus should be usability, as it encompasses the former. If you have good usability you can involve the player in emotions; Thus, create a successful game.
Bolt Peters and EA Software undertook a year long testing project for their much talked about game “Spore” with an usability approach in mind. Check this article by Nate Bolt and Tony Tulathimutte for the Boxes and arrows blog to find out all the details of their UX testing approach. Plenty of information and even videos are included. Fantastic post!