Foo.hs

module RankingSpec(spec) where

import Test.Hspec(describe, Spec)
import Test.Hspec.QuickCheck(prop)
import Test.QuickCheck(applyFun2, Fun)
import qualified Data.List.NonEmpty            as NE
import Myocardio.Ranking(generateComplements)
import Test.QuickCheck.Instances.Semigroup

propType :: [a] -> Fun (a,NE.NonEmpty a) Int -> Bool
propType as f = length (generateComplements as (applyFun2 f)) == length as

spec :: Spec
spec =
    describe "generate complements" $
        prop "should never change the number of list elements" propType

{-
test-suite/RankingSpec.hs:16:9: error:

    • Ambiguous type variable ‘a0’ arising from a use of ‘prop’

      prevents the constraint ‘(Test.QuickCheck.Arbitrary.Arbitrary

                                  a0)’ from being solved.

      Probable fix: use a type annotation to specify what ‘a0’ should be.

      These potential instances exist:

        instance [safe] (Test.QuickCheck.Function.Function a,

                         Test.QuickCheck.Arbitrary.CoArbitrary a,

                         Test.QuickCheck.Arbitrary.Arbitrary b) =>

                        Test.QuickCheck.Arbitrary.Arbitrary (Fun a b)

          -- Defined in ‘Test.QuickCheck.Function’

        instance (Test.QuickCheck.Arbitrary.Arbitrary a,

                  Test.QuickCheck.Arbitrary.Arbitrary b) =>

                 Test.QuickCheck.Arbitrary.Arbitrary (Either a b)

          -- Defined in ‘Test.QuickCheck.Arbitrary’

        instance [safe] Test.QuickCheck.Arbitrary.Arbitrary a =>

                        Test.QuickCheck.Arbitrary.Arbitrary (NE.NonEmpty a)

          -- Defined in ‘Test.QuickCheck.Instances.Semigroup’

        ...plus 21 others

        ...plus 75 instances involving out-of-scope types

        (use -fprint-potential-instances to see them all)

    • In a stmt of a 'do' block:

        prop "should never change the number of list elements" propType

      In the second argument of ‘($)’, namely

        ‘do prop

              "should never change the number of list elements" propType’

      In the expression:

        describe "generate complements"

          $ do prop

                 "should never change the number of list elements" propType

   |

16 |         prop "should never change the number of list elements" propType

   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-}