[QuickCheck] How to evaluate a Property?

[Nick Smallbone]

Hi Bryan,

If your properties are just functions which return Property instead of
Bool, then you can just use quickCheck to evaluate them on a
particular input. Example:

    prop_bogus :: Int -> Int -> Property
    prop_bogus x y = x === y

    > quickCheck prop_bogus
    *** Failed! Falsifiable (after 2 tests):                  
    1
    0
    1 /= 0
    > quickCheck (prop_bogus 3)
    *** Failed! Falsifiable (after 1 test):  
    0
    3 /= 0
    > quickCheck (prop_bogus 3 3)
    +++ OK, passed 100 tests.
    > quickCheck (prop_bogus 3 4)
    *** Failed! Falsifiable (after 1 test):  
    3 /= 4

If you start using explicit forAlls and whatnot, then you're probably
out of luck (short of refactoring), as a Property is just a function
from random number seed to test outcome, and the only thing you can
sensibly do is pass it to quickCheck.

Nick

On Friday 13 June, 2014 at 01:26 pm, Bryan O'Sullivan wrote:
> A downside of switching from Bool-typed to Property-typed tests is that I
> have no idea how to evaluate a Property by hand at the ghci command line.
> If I'm doing some narrowly directed testing by hand while I iterate on a
> bug, that can significantly slow me down.
> 
> I realise that this is probably not achievable in general, but for instance
> many of my tests are simple ones involving (===), (.&&.) and the like, with
> no fanciness needed.
> 
> Thanks!

> _______________________________________________
> QuickCheck mailing list
> QuickCheck at projects.haskell.org
> http://projects.haskell.org/cgi-bin/mailman/listinfo/quickcheck