duncan.coutts:
On Sun, 2006-10-08 at 15:25 -0700, Jason Dagit wrote:
Another good idea when you have a pretty version which is easy to verify for correctness and an ugly version that is harder to verify is to use QuickCheck or SmallCheck and define a property that says both versions are equal for all inputs. Ugly code is notorious for holding bugs, but doing this would help test the ugly code.
This is exactly how we tested Data.ByteString and to great effect I think. We uncovered loads of bugs during testing. The few bugs uncovered by our users since it has been released have invariably been in things we didn't have QC properties for.
Yes, I agree with this. By checking fast-bug-ugly code against slow-but-obvious code, we were able to catch bugs before Data.ByteString was deployed in the outside world, and before the bugs could hurt anyone. These days, Data.ByteString has some 2000 lines of QC properties, which are run on ever darcs commit. -- Don