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25 lines
788 B
Haskell
25 lines
788 B
Haskell
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-- | Defines useful Hedgehog checkers based around the properties of
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-- standard typeclasses (associativity, reflexivity, etc.) This module
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-- is similar to the hedgehog-checkers package on Hackage, but said
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-- package doesn't work with hedgehog-1.0, so we reproduce these
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-- (largely-trivial) functions here.
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module Properties
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( associative
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, monoidal
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) where
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import Hedgehog
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import GHC.Stack
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associative :: (Eq a, Show a) => (a -> a -> a) -> Gen a -> Property
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associative fn gen = property . withFrozenCallStack $ do
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(a, b, c) <- forAll ((,,) <$> gen <*> gen <*> gen)
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fn a (fn b c) === fn (fn a b) c
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monoidal :: (Eq a, Show a, Monoid a) => Gen a -> Property
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monoidal gen = property . withFrozenCallStack $ do
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it <- forAll gen
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mempty <> it === it
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it <> mempty === it
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