QuickCheck-2.8.1: Automatic testing of Haskell programs

Safe HaskellSafe
LanguageHaskell98

Test.QuickCheck.Gen

Contents

Description

Test case generation.

Synopsis

Generator type

newtype Gen a Source

A generator for values of type a.

Constructors

MkGen 

Fields

unGen :: QCGen -> Int -> a

Run the generator on a particular seed. If you just want to get a random value out, consider using generate.

Instances

Primitive generator combinators

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

Modifies a generator using an integer seed.

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

Used to construct generators that depend on the size parameter.

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

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

scale :: (Int -> Int) -> Gen a -> Gen a Source

Adjust the size parameter, by transforming it with the given function.

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

Generates a random element in the given inclusive range.

generate :: Gen a -> IO a Source

Run a generator. The size passed to the generator is always 30; if you want another size then you should explicitly use resize.

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

Generates some example values.

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

Generates some example values and prints them to stdout.

Common generator combinators

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

Generates a value that satisfies a predicate.

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

Tries to generate a value that satisfies a predicate.

oneof :: [Gen a] -> Gen a Source

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

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

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

elements :: [a] -> Gen a Source

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

sublistOf :: [a] -> Gen [a] Source

Generates a random subsequence of the given list.

shuffle :: [a] -> Gen [a] Source

Generates a random permutation of the given list.

growingElements :: [a] -> Gen a Source

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] Source

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

listOf1 :: Gen a -> Gen [a] Source

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

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

Generates a list of the given length.

infiniteListOf :: Gen a -> Gen [a] Source

Generates an infinite list.