But it doesn't follow that changing a unit's interface means unit tests suddenly become just a burden. Ideally unit tests are, well, testing a bunch of core functionality of the unit under test. You adapt them to the new interface. Then you're back to having a quick, automatic sanity check you can run against the unit whenever you have to make a change.

I don't understand people bemoaning this 'cost' of unit tests when the benefits they provide typically far outweigh the costs. It's possible broader functional/integration tests have a better ROI in certain situations, but they come with a maintenance cost as well.

If your refactoring is largely centered around changing unit interfaces (not uncommon) then it means that those unit tests are 100% overhead because most of the time they fail just because you changed the code.

>I don't understand people bemoaning this 'cost' of unit tests when the benefits they provide typically far outweigh the costs. It's possible broader functional/integration tests have a better ROI in certain situations, but they come with a maintenance cost as well.

I've certainly found that the ROI is a lot better. I find that integration tests have a higher up-front cost but maintenance-wise they're the same or cheaper. % of failures that are actually catching bugs is higher too.