I've found unit tests valuable as executable documentation for inner interfaces that manual testing can't reach easily Say I've got some algorithm like a binar

I've found unit tests valuable as executable documentation for inner interfaces that manual testing can't reach easily Say I've got some algorithm like a binary search that you can implement in a page of code but it's gonna be buried three layers deep in the business logic. You could expose a debug command and test it manually, or you could throw a few unit tests on it to hit all the edge cases, make sure it gives the expected outputs for given inputs, and then you know there aren't major bugs there