QuickCheck properties for IntSet

[Don Stewart]

igloo:
> On Sun, Dec 09, 2007 at 01:25:48AM -0800, David Benbennick wrote:
> > On 12/8/07, David Benbennick <dbenbenn at gmail.com> wrote:
> > > I commented out some code that could never be executed:
> > > * Some case-statement cases that could never occur.
> > > * >>= for the Identity monad used internally.
> > 
> > Sorry, I forgot to run the "validate" script on the previous patch.
> > Turns out validate requires >>= to be explicitly set, even though it
> > isn't used.  New patch bundle is attached.
> 
> Sorry, I've had this sitting in my mailbox for some time, but only just
> got around to looking at it properly. Thanks for writing it!
> 
> If I export test_all and make a program that runs it then it takes
> almost exactly 1 minute to test this one module, as compared to 19
> minutes to run the whole testsuite in fast mode, so I don't think that
> running this as part of the fast testsuite is feasible.
> 
> I am not even convinced that it makes sense to run it as part of the
> full testsuite - I don't think we can afford to spend an hour for every
> 60 modules that we want to test.
> 
> You might claim that it is taking so long because it is testing IntSet
> thoroughly, but I claim that it is merely testing it a lot (and, I
> suspect, testing some cases many times). I believe that a much smaller
> number of carefully chosen unit tests could test the library just as
> well, and two or three orders of magnitude more quickly. I hope that
> soonish we will add hpc support to the testsuite, so we can signal a
> failure if we don't get 100% coverage.
> 
> So, in conclusion, I don't think that we should apply this patch (or,
> more generally, use QC tests in the testsuite).
> 

What if we used QC tests with SmallCheck generators, so you 
actually got decent search through the value space, rather than
just a random walk?

Or if QC only did, say, 10 tests deep, but with a random seed (should
take a fraction of a second, but over time you'll end up testing an
awful lot of the inhabitants)

I usuually run QuickCheck depth 10 on every single commit with
bytestring, uvector, xmonad. Its not burdensome.

-- Don