On 2004-01-01 at 21:07EST ajb@spamcop.net wrote:
There is only one problem I've found with test-driven development in Haskell. In C++, it's possible to break the "module" abstraction (yes, I know, C++ doesn't have modules; it has classes, which are really instantiable modules) by using "friend". In Haskell, I find myself occasionally having to expose parts of a module which I would prefer not to, in order for the unit tests suite to do their job effectively.
I wonder if there might be a way to fix this, say, by allowing modules to selectively expose parts of their interface depending on who wants to use it.
One of my unexplored ideas is to make tests part of the code of a module (probably best done with some sort of typed include mechanism for test data), linked in some way with the type of an entity. So one might write something like f :: Integer -> Integer |? f 0 == 1 && f 3 == 6 The compiler would then (optionally?) run the tests as part of the compilation. This would bind the tests more tightly to the programme than is now possible. As I say, I haven't explored this, so perhaps some of those agile minds out there could run with it? -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk