The best use case I see for this is when you inherit a testless codebase. It's a way to get bootstrapped, and go from there. Sometimes you have to honor bugs

The best use case I see for this is when you inherit a testless codebase. It's a way to get bootstrapped, and go from there. Sometimes you have to honor bugs as part of the (undocumented/evolved/inferred) interface. It could help to discover these, walk through them and see where they can be fixed or where they need to be honored. It could also help prevent the "rewrite from scratch because I don't understand it" problem. Heck, I've even done that to myself picking up a codebase I haven't touched in 3+ years, sometimes validly, sometimes notsomuch. I'll have to see how it works next time this happens to me, because this is pure conjecture.