Explain HOW that's irrelevant.
Debug the code? Are you serious? That is a ridiculous argument.How do you know what's best? You could debug it like a normal person would when they change their own code. C++ is not one of those happy languages where if it compiles it automatically works. In fact I don't think there is a language like that. You still have to care about what happens in run time no matter what.
Debugging isn't meant to make sure the code works. It's meant to FIND what causes the bugs that prevents the coding from working.
Regression testing makes sure the code works. This is part of regression testing.
It also creates fewer bugs, and it decreases the likelihood of bugs escaping notice.
It does not, however, mean that you should rely ONLY on this. This is meant to be a tool to complement your arsenal, not replace it.