Do this thing in 3 ways, do that one in 4, do another one in 2 and you have 3x4x2 = 24 combinations which are entirely gratuitous compared to the 1 combination that exists if all three things are done one way each.

Oh, you don't have to test the combinations because the code is bug free, is that the argument? Which is because of some good organization?

Those things are nicely isolated so 3 + 4 + 2 unit tests, and we are done?