> but practitioners don't care about the answer to that question because they don't care about that question at all. They want to know how best to do Y, period.

> but practitioners don't care about the answer to that question because they don't care about that question at all. They want to know how best to do Y, period. OK, I'll bite. If the entirety of your goal is to do Y, you will never write a single test. Why would you write a test? It doesn't "do Y", for whichever Y is producing profit or some other benefit for you. Real, True Scotsmen understand that how to do Y is important, because it makes sure that they'll be able to do Z tomorrow. Tests are not essential for functional systems, they are essential for maintainable systems. Types are just tests enforced by the compiler. Every type-level tool that Haskell gives you is just another tool that makes it easier to write tests that actually help prove that your code is still working. Half the problem with our industry is that no other industry would accept unmaintainable product. Too many practicioners are practically proud of all their rewrites and green-field projects.