I've found similar systems to be very useful in certain situations, including: refactoring, rapidly changing code bases, and code that doesn't have enough unit

I've found similar systems to be very useful in certain situations, including: refactoring, rapidly changing code bases, and code that doesn't have enough unit tests. Yes, all of these situations could be improved by having more unit tests, but systems like these have an extremely high bang-buck ratio. They're extremely cheap to put in, and they some bugs.