Yes, maybe it's the wrong abstraction or it won't match in 6 months because people will start calling Hats Pizzas and the logic will be different. Maybe I'll be dead tomorrow. I don't concern myself with what-ifs over unknowns.

I want correctness and some assurance of it. I don't think writing 50? tests to cover this thing is a good way to spend my time (or someone else's). I'll write the left hand side first. When I'm looking at writing tests, it will become something like the right hand side.

Yes linear code is more readable. That's something to consider, but it's not my primary consideration.