I think the key distinction there is - you'd ship the games, and never change them again. What the tests do is let you continually evolve the software over a l

I think the key distinction there is - you'd ship the games, and never change them again. What the tests do is let you continually evolve the software over a long period of time. What you need tests for is to give you confidence that chaning system a doesn't impact system b negatively, allowing the software to continue evolving at a much faster pace once you have a good test suite in place.