On Mon, Aug 10, 2009 at 4:20 PM, Srikanth K wrote:

Hi,    I am trying to use the quickcheck to generate some test-data to test an api, along the lines of http://www.haskell.org/haskellwiki/QuickCheck_as_Test_Set_Generator.

For the sake of example, I choose the following function to test

data Result = Valid | Invalid api_under_test :: (Int,Int) ->  Result api_under_test (x,y)    | (x == 1)  =   Valid    | otherwise = Invalid

I had the following valid-generator which worked quite easily(trivial)

validCombinations= [ (1,1), (1,2) ] validGen = elements validCombinations prop_valid_api_under_test =     forAll validGen $ \xs ->          (api_under_test xs) == (Valid)

Now, I want to have a complement to state:      forall tuples not in validCombinations, the api_under_test must return "Invalid".  (i.e.)

prop_invalid_api_under_test =     forAll invalidGen $ \xs ->         (api_under_test xs) == (Invalid)

However, inspite of all  googling, and reading the various docs including quickcheck, I am at loss on how I can elegantly define the "invalidGen" generator.  One possible way I can think is to have a customized generator, that would generate two random numbers and then look up the tuple generated against the validCombinations list.

However, I feel there just might be a better way of solving this.

Any suggestion on how I should be trying to solve this.

- Srikanth _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

The way I would do this is (untested) prop_invalid_api_under_test xs = not (xs `elem` validCombinations) ==> api_under_test xs = Invalid using the (==>) function from QuickCheck. Alex