Safe Haskell	Safe
Language	Haskell2010

Test.QuickCheck.Monadic

Contents

Property monad
Monadic specification combinators
Run functions

Description

Allows testing of monadic values. Will generally follow this form:

prop_monadic a b = monadicIO $ do
  a' <- run (f a)
  b' <- run (f b)
  -- ...
  assert someBoolean

Example using the FACTOR(1) command-line utility:

import System.Process
import Test.QuickCheck
import Test.QuickCheck.Monadic

-- $ factor 16
-- 16: 2 2 2 2
factor :: Integer -> IO [Integer]
factor n = parse `fmap` readProcess "factor" [show n] "" where

  parse :: String -> [Integer]
  parse = map read . tail . words

prop_factor :: Positive Integer -> Property
prop_factor (Positive n) = monadicIO $ do
  factors <- run (factor n)

  assert (product factors == n)

>>> quickCheck prop_factor
+++ OK, passed 100 tests.

See the paper " Testing Monadic Code with QuickCheck ".

Synopsis

newtype PropertyM m a = MkPropertyM {
- unPropertyM :: (a -> Gen (m Property )) -> Gen (m Property )
}
run :: Monad m => m a -> PropertyM m a
assert :: Monad m => Bool -> PropertyM m ()
pre :: Monad m => Bool -> PropertyM m ()
wp :: Monad m => m a -> (a -> PropertyM m b) -> PropertyM m b
pick :: ( Monad m, Show a) => Gen a -> PropertyM m a
forAllM :: ( Monad m, Show a) => Gen a -> (a -> PropertyM m b) -> PropertyM m b
monitor :: Monad m => ( Property -> Property ) -> PropertyM m ()
stop :: ( Testable prop, Monad m) => prop -> PropertyM m a
monadic :: ( Testable a, Monad m) => (m Property -> Property ) -> PropertyM m a -> Property
monadic' :: ( Testable a, Monad m) => PropertyM m a -> Gen (m Property )
monadicIO :: Testable a => PropertyM IO a -> Property
monadicST :: Testable a => ( forall s. PropertyM ( ST s) a) -> Property
runSTGen :: ( forall s. Gen ( ST s a)) -> Gen a

Property monad

newtype PropertyM m a Source #

The property monad is really a monad transformer that can contain monadic computations in the monad m it is parameterized by:

m - the m -computations that may be performed within PropertyM

Elements of PropertyM m a may mix property operations and m -computations.

Constructors

MkPropertyM
Fields unPropertyM :: (a -> Gen (m Property )) -> Gen (m Property )

Instances

Instances details

MonadTrans PropertyM Source #
Instance details Defined in Test.QuickCheck.Monadic Methods lift :: Monad m => m a -> PropertyM m a Source #
Monad m => Monad ( PropertyM m) Source #
Instance details Defined in Test.QuickCheck.Monadic Methods (>>=) :: PropertyM m a -> (a -> PropertyM m b) -> PropertyM m b Source # (>>) :: PropertyM m a -> PropertyM m b -> PropertyM m b Source # return :: a -> PropertyM m a Source #
Functor ( PropertyM m) Source #
Instance details Defined in Test.QuickCheck.Monadic Methods fmap :: (a -> b) -> PropertyM m a -> PropertyM m b Source # (<$) :: a -> PropertyM m b -> PropertyM m a Source #
Monad m => MonadFail ( PropertyM m) Source #
Instance details Defined in Test.QuickCheck.Monadic Methods fail :: String -> PropertyM m a Source #
Applicative ( PropertyM m) Source #
Instance details Defined in Test.QuickCheck.Monadic Methods pure :: a -> PropertyM m a Source # (<>) :: PropertyM m (a -> b) -> PropertyM m a -> PropertyM m b Source # liftA2 :: (a -> b -> c) -> PropertyM m a -> PropertyM m b -> PropertyM m c Source # (>) :: PropertyM m a -> PropertyM m b -> PropertyM m b Source # (<*) :: PropertyM m a -> PropertyM m b -> PropertyM m a Source #
MonadIO m => MonadIO ( PropertyM m) Source #
Instance details Defined in Test.QuickCheck.Monadic Methods liftIO :: IO a -> PropertyM m a Source #

Monadic specification combinators

run :: Monad m => m a -> PropertyM m a Source #

The lifting operation of the property monad. Allows embedding monadic/ IO -actions in properties:

log :: Int -> IO ()

prop_foo n = monadicIO $ do
  run (log n)
  -- ...

assert :: Monad m => Bool -> PropertyM m () Source #

Allows embedding non-monadic properties into monadic ones.

pre :: Monad m => Bool -> PropertyM m () Source #

Tests preconditions. Unlike assert this does not cause the property to fail, rather it discards them just like using the implication combinator ==> .

This allows representing the Hoare triple

{p} x ← e{q}

as

pre p
x <- run e
assert q

wp :: Monad m => m a -> (a -> PropertyM m b) -> PropertyM m b Source #

The weakest precondition

wp(x ← e, p)

can be expressed as in code as wp e (\x -> p) .

pick :: ( Monad m, Show a) => Gen a -> PropertyM m a Source #

Quantification in a monadic property, fits better with do-notation than forAllM . Note : values generated by pick do not shrink.

forAllM :: ( Monad m, Show a) => Gen a -> (a -> PropertyM m b) -> PropertyM m b Source #

Quantification in monadic properties to pick , with a notation similar to forAll . Note : values generated by forAllM do not shrink.

monitor :: Monad m => ( Property -> Property ) -> PropertyM m () Source #

Allows making observations about the test data:

monitor (collect e)

collects the distribution of value of e .

monitor (counterexample "Failure!")

Adds "Failure!" to the counterexamples.

stop :: ( Testable prop, Monad m) => prop -> PropertyM m a Source #

Run functions

monadic :: ( Testable a, Monad m) => (m Property -> Property ) -> PropertyM m a -> Property Source #

monadic' :: ( Testable a, Monad m) => PropertyM m a -> Gen (m Property ) Source #

monadicIO :: Testable a => PropertyM IO a -> Property Source #

Runs the property monad for IO -computations.

prop_cat msg = monadicIO $ do
  (exitCode, stdout, _) <- run (readProcessWithExitCode "cat" [] msg)

  pre (ExitSuccess == exitCode)

  assert (stdout == msg)

>>> quickCheck prop_cat
+++ OK, passed 100 tests.

monadicST :: Testable a => ( forall s. PropertyM ( ST s) a) -> Property Source #

Runs the property monad for ST -computations.

-- Your mutable sorting algorithm here
sortST :: Ord a => [a] -> ST s (MVector s a)
sortST = thaw . fromList . sort

prop_sortST xs = monadicST $ do
  sorted  <- run (freeze =<< sortST xs)
  assert (toList sorted == sort xs)

>>> quickCheck prop_sortST
+++ OK, passed 100 tests.

runSTGen :: ( forall s. Gen ( ST s a)) -> Gen a Source #