On Wed, Jan 5, 2011 at 3:02 PM, Jonathan Geddes
The Haskell type system is simply not rich enough to guarantee everything you might need. Despite all this, I suspect that since Haskell is at a higher level of abstraction than other languages, the tests in Haskell must be at a correspondingly higher level than the tests in other languages. I can see that such tests would give great benefits to the development process. I am convinced that I should try to write such tests. But I still think that Haskell makes a huge class of tests unnecessary.
The way I think about this is that you want to write tests for things that can not be usefully represented in the type system. If you have a parametrically typed function, then the type system is doing a lot of useful "testing" for you. If you want to make sure that you properly parse documents in a given format, then having a bunch of examples that feed into unit tests is a smart move. Anthony