> "If I don't typically make a kind of mistake (like setting the wrong variables in a constructor), I don't test for it."

Hmm, that sounds like the old "You don't need to test , just be an awesome programmer duh!" argument.

The kind of mistakes you never anticipate making are probably the sort of stuff you should be testing for.

The amount of times I've had something fail on an edge case that turned out to be a typo in a var name on some edge case somewhere..