Test.QuickCheck.Gen

Test case generation

Generator type

newtype Gen a

Constructors

MkGen

Fields

unGen :: StdGen -> Int -> a

Instances

Monad Gen

Functor Gen

Applicative Gen

Testable prop => Testable (Gen prop)

Primitive generator combinators

variant :: Integral n => n -> Gen a -> Gen a

Modifies a generator using an integer seed.

sized :: (Int -> Gen a) -> Gen a

Used to construct generators that depend on the size parameter.

resize :: Int -> Gen a -> Gen a

Overrides the size parameter. Returns a generator which uses the given size instead of the runtime-size parameter.

choose :: Random a => (a, a) -> Gen a

Generates a random element in the given inclusive range.

promote :: Monad m => m (Gen a) -> Gen (m a)

Promotes a generator to a generator of monadic values.

sample' :: Gen a -> IO [a]

Generates some example values.

sample :: Show a => Gen a -> IO ()

Generates some example values and prints them to stdout.

Common generator combinators

suchThat :: Gen a -> (a -> Bool) -> Gen a

Generates a value that satisfies a predicate.

suchThatMaybe :: Gen a -> (a -> Bool) -> Gen (Maybe a)

Tries to generate a value that satisfies a predicate.

oneof :: [Gen a] -> Gen a

Randomly uses one of the given generators. The input list must be non-empty.

frequency :: [(Int, Gen a)] -> Gen a

Chooses one of the given generators, with a weighted random distribution. The input list must be non-empty.

elements :: [a] -> Gen a

Generates one of the given values. The input list must be non-empty.

growingElements :: [a] -> Gen a

Takes a list of elements of increasing size, and chooses among an initial segment of the list. The size of this initial segment increases with the size parameter. The input list must be non-empty.

listOf :: Gen a -> Gen [a]

Generates a list of random length. The maximum length depends on the size parameter.

listOf1 :: Gen a -> Gen [a]

Generates a non-empty list of random length. The maximum length depends on the size parameter.

vectorOf :: Int -> Gen a -> Gen [a]

Generates a list of the given length.