Thats cool. Its no surprise that SUnit came from the untyped world – I do believe it was to act as the safty net lost from static typing.

http://lambda-the-ultimate.org/node/1827

You can write a logical specification of what a function should produce (e.g.: sqrt(X) = Y such that Y * Y = X), and QuickCheck generates test cases. When it finds a contradiction, it reduces the failing test case to its simplest form and reports it to you.

Working with these things in untyped languages though, I sometimes get the feeling that I’m just plugging up holes in the language’s (absent) type system. You can’t statically verify everything of course, but there’s a lot more that we can do to eliminate the need to test whole categories of problems at runtime.