genvalidity-hspec-1.0.0.4: src/Test/Validity/Arbitrary.hs

{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeApplications #-}

-- | Tests for Arbitrary instances involving Validity
--
-- You will need @TypeApplications@ to use these.
module Test.Validity.Arbitrary
  ( arbitrarySpec,
    arbitraryGeneratesOnlyValid,
  )
where

import Data.Data
import Data.GenValidity
import Test.Hspec
import Test.QuickCheck
import Test.Validity.GenValidity
import Test.Validity.Utils

-- | A @Spec@ that specifies that @arbitrary@ only generates data that
-- satisfy @isValid@
--
-- Example usage:
--
-- > arbitrarySpec @Int
arbitrarySpec ::
  forall a.
  (Typeable a, Show a, Validity a, Arbitrary a) =>
  Spec
arbitrarySpec = do
  let name = nameOf @a
  describe ("Arbitrary " ++ name) $
    describe ("arbitrary :: Gen " ++ name) $
      it "only generates valid values" $
        arbitraryGeneratesOnlyValid @a

-- | @arbitrary@ only generates valid data
--
-- prop> arbitraryGeneratesOnlyValid @Int
arbitraryGeneratesOnlyValid ::
  forall a.
  (Show a, Validity a, Arbitrary a) =>
  Property
arbitraryGeneratesOnlyValid = genGeneratesValid @a arbitrary