deque-blog’s gists

deque-blog / rapid_check_3_forall.hs

Last active February 8, 2017 14:11

	forAll :: (Show a, Testable testable)
	=> Gen a -> Shrink a -> (a -> testable) -> Property
	forAll argGen shrink prop = ...

deque-blog / rapid_check_3_find_failing.hs

Last active February 8, 2017 14:08

	findFailing :: [a] -> (a -> Result) -> Maybe (a, Result)
	findFailing smaller runSub =
	let results = map runSub smaller
	in find (isFailure . snd) (zip smaller results)

deque-blog / rapid_check_3_shrink_inputs.hs

Created February 8, 2017 17:22

	shrinking :: (Show a) => Shrink a -> a -> (a -> Result) -> Result
	shrinking = undefined

deque-blog / rapid_check_3_eval_sub_prop.hs

Created February 8, 2017 17:29

	evalSubProp :: Testable t => (a -> t) -> StdGen -> a -> Result
	evalSubProp prop rand = (`runProp` rand) . property . prop

deque-blog / rapid_check_3_invalid_prop.hs

Created February 9, 2017 17:23

	prop_gcd_bad :: Integer -> Integer -> Bool
	prop_gcd_bad a b = gcd a b > 1

deque-blog / rapid_check_4_result_tree.hs

Last active February 10, 2017 10:52

	data Tree a = Tree
	{ treeVal :: a
	, children :: [Tree a] }
	deriving (Functor)

	newtype Property = Property { getGen :: Gen (Tree Result) }

deque-blog / rapid_check_4_visit_result_tree.hs

Created February 10, 2017 10:45

	visitResultTree :: Tree Result -> Result
	visitResultTree (Tree Success _) = Success
	visitResultTree (Tree failure children) =
	let simplerFailure = find (isFailure . treeVal) children
	in maybe failure visitResultTree simplerFailure

deque-blog / rapid_check_4_rapid_check.hs

Created February 10, 2017 10:48

	rapidCheckImpl :: Testable prop => Int -> Int -> prop -> Result
	rapidCheckImpl attemptNb startSeed prop = runAll (property prop)
	where
	runAll prop = foldMap (runOne prop) [startSeed .. startSeed + attemptNb - 1]
	runOne prop seed =
	let result = visitResultTree (runProp prop (mkStdGen seed))
	in overFailure result $ \failure -> failure { seed = seed }

deque-blog / rapid_check_4_for_all.hs

Last active February 10, 2017 10:59

	forAll :: (Show a, Testable t) => Gen a -> Shrink a -> (a -> t) -> Property
	forAll argGen shrink prop =
	Property $ Gen $ \rand -> -- Create a new property that will
	let (rand1, rand2) = split rand -- Split the generator in two
	arg = runGen argGen rand1 -- Use the first generator to produce an arg
	tree = resultTree shrink arg prop -- Enrich the sub-property result tree
	in runProp tree rand2 -- Run the property with the second generator

deque-blog / rapid_check_4_result_tree_build.hs

Last active February 10, 2017 12:14

	resultTree :: (Show a, Testable t) => Shrink a -> a -> (a -> t) -> Property
	resultTree shrinker arg prop =
	Property $ Gen $ \rand ->
	let shrinkTree = buildTree shrinker arg -- Build the shrink tree
	resultTree = fmap toResult shrinkTree -- Transform it to a result tree
	toResult x = -- To compute a result tree
	addCounterExample x $ -- Add the outer arg to all failures
	runProp (property (prop x)) rand -- Inside the sub result tree
	in joinTree resultTree -- At the end, join the result tree