"But we don't write tests to check if our code works." If the input data is complex enough to drive a non-trivial branching logic in our code - yes we do. Well

"But we don't write tests to check if our code works." If the input data is complex enough to drive a non-trivial branching logic in our code - yes we do. Well, at least I do. The bonus is that it provides the fixed point for further changes at the same time.