QuickCheck-2.12.6.1: Automatic testing of Haskell programs

Safe HaskellTrustworthy
LanguageHaskell98

Test.QuickCheck.Arbitrary

Contents

Description

Type classes for random generation of values.

Note: the contents of this module are re-exported by Test.QuickCheck. You do not need to import it directly.

Synopsis

Arbitrary and CoArbitrary classes

class Arbitrary a where #

Random generation and shrinking of values.

QuickCheck provides Arbitrary instances for most types in base, except those which incur extra dependencies. For a wider range of Arbitrary instances see the quickcheck-instances package.

Minimal complete definition

arbitrary

Methods

arbitrary :: Gen a #

A generator for values of the given type.

It is worth spending time thinking about what sort of test data you want - good generators are often the difference between finding bugs and not finding them. You can use sample, label and classify to check the quality of your test data.

There is no generic arbitrary implementation included because we don't know how to make a high-quality one. If you want one, consider using the testing-feat or generic-random packages.

The QuickCheck manual goes into detail on how to write good generators. Make sure to look at it, especially if your type is recursive!

shrink :: a -> [a] #

Produces a (possibly) empty list of all the possible immediate shrinks of the given value.

The default implementation returns the empty list, so will not try to shrink the value. If your data type has no special invariants, you can enable shrinking by defining shrink = genericShrink, but by customising the behaviour of shrink you can often get simpler counterexamples.

Most implementations of shrink should try at least three things:

  1. Shrink a term to any of its immediate subterms. You can use subterms to do this.
  2. Recursively apply shrink to all immediate subterms. You can use recursivelyShrink to do this.
  3. Type-specific shrinkings such as replacing a constructor by a simpler constructor.

For example, suppose we have the following implementation of binary trees:

data Tree a = Nil | Branch a (Tree a) (Tree a)

We can then define shrink as follows:

shrink Nil = []
shrink (Branch x l r) =
  -- shrink Branch to Nil
  [Nil] ++
  -- shrink to subterms
  [l, r] ++
  -- recursively shrink subterms
  [Branch x' l' r' | (x', l', r') <- shrink (x, l, r)]

There are a couple of subtleties here:

  • QuickCheck tries the shrinking candidates in the order they appear in the list, so we put more aggressive shrinking steps (such as replacing the whole tree by Nil) before smaller ones (such as recursively shrinking the subtrees).
  • It is tempting to write the last line as [Branch x' l' r' | x' <- shrink x, l' <- shrink l, r' <- shrink r] but this is the wrong thing! It will force QuickCheck to shrink x, l and r in tandem, and shrinking will stop once one of the three is fully shrunk.

There is a fair bit of boilerplate in the code above. We can avoid it with the help of some generic functions. The function genericShrink tries shrinking a term to all of its subterms and, failing that, recursively shrinks the subterms. Using it, we can define shrink as:

shrink x = shrinkToNil x ++ genericShrink x
  where
    shrinkToNil Nil = []
    shrinkToNil (Branch _ l r) = [Nil]

genericShrink is a combination of subterms, which shrinks a term to any of its subterms, and recursivelyShrink, which shrinks all subterms of a term. These may be useful if you need a bit more control over shrinking than genericShrink gives you.

A final gotcha: we cannot define shrink as simply shrink x = Nil:genericShrink x as this shrinks Nil to Nil, and shrinking will go into an infinite loop.

If all this leaves you bewildered, you might try shrink = genericShrink to begin with, after deriving Generic for your type. However, if your data type has any special invariants, you will need to check that genericShrink can't break those invariants.

Instances

Arbitrary Bool # 

Methods

arbitrary :: Gen Bool #

shrink :: Bool -> [Bool] #

Arbitrary Char # 

Methods

arbitrary :: Gen Char #

shrink :: Char -> [Char] #

Arbitrary Double # 
Arbitrary Float # 

Methods

arbitrary :: Gen Float #

shrink :: Float -> [Float] #

Arbitrary Int # 

Methods

arbitrary :: Gen Int #

shrink :: Int -> [Int] #

Arbitrary Int8 # 

Methods

arbitrary :: Gen Int8 #

shrink :: Int8 -> [Int8] #

Arbitrary Int16 # 

Methods

arbitrary :: Gen Int16 #

shrink :: Int16 -> [Int16] #

Arbitrary Int32 # 

Methods

arbitrary :: Gen Int32 #

shrink :: Int32 -> [Int32] #

Arbitrary Int64 # 

Methods

arbitrary :: Gen Int64 #

shrink :: Int64 -> [Int64] #

Arbitrary Integer # 
Arbitrary Ordering # 
Arbitrary Word # 

Methods

arbitrary :: Gen Word #

shrink :: Word -> [Word] #

Arbitrary Word8 # 

Methods

arbitrary :: Gen Word8 #

shrink :: Word8 -> [Word8] #

Arbitrary Word16 # 
Arbitrary Word32 # 
Arbitrary Word64 # 
Arbitrary () # 

Methods

arbitrary :: Gen () #

shrink :: () -> [()] #

Arbitrary Version #

Generates Version with non-empty non-negative versionBranch, and empty versionTags

Arbitrary ExitCode # 
Arbitrary CChar # 

Methods

arbitrary :: Gen CChar #

shrink :: CChar -> [CChar] #

Arbitrary CSChar # 
Arbitrary CUChar # 
Arbitrary CShort # 
Arbitrary CUShort # 
Arbitrary CInt # 

Methods

arbitrary :: Gen CInt #

shrink :: CInt -> [CInt] #

Arbitrary CUInt # 

Methods

arbitrary :: Gen CUInt #

shrink :: CUInt -> [CUInt] #

Arbitrary CLong # 

Methods

arbitrary :: Gen CLong #

shrink :: CLong -> [CLong] #

Arbitrary CULong # 
Arbitrary CLLong # 
Arbitrary CULLong # 
Arbitrary CFloat # 
Arbitrary CDouble # 
Arbitrary CPtrdiff # 
Arbitrary CSize # 

Methods

arbitrary :: Gen CSize #

shrink :: CSize -> [CSize] #

Arbitrary CWchar # 
Arbitrary CSigAtomic # 
Arbitrary CClock # 
Arbitrary CTime # 

Methods

arbitrary :: Gen CTime #

shrink :: CTime -> [CTime] #

Arbitrary CUSeconds # 
Arbitrary CSUSeconds # 
Arbitrary CIntPtr # 
Arbitrary CUIntPtr # 
Arbitrary CIntMax # 
Arbitrary CUIntMax # 
Arbitrary All # 

Methods

arbitrary :: Gen All #

shrink :: All -> [All] #

Arbitrary Any # 

Methods

arbitrary :: Gen Any #

shrink :: Any -> [Any] #

Arbitrary IntSet # 
Arbitrary PrintableString # 
Arbitrary UnicodeString # 
Arbitrary ASCIIString # 
Arbitrary OrdC # 

Methods

arbitrary :: Gen OrdC #

shrink :: OrdC -> [OrdC] #

Arbitrary OrdB # 

Methods

arbitrary :: Gen OrdB #

shrink :: OrdB -> [OrdB] #

Arbitrary OrdA # 

Methods

arbitrary :: Gen OrdA #

shrink :: OrdA -> [OrdA] #

Arbitrary C # 

Methods

arbitrary :: Gen C #

shrink :: C -> [C] #

Arbitrary B # 

Methods

arbitrary :: Gen B #

shrink :: B -> [B] #

Arbitrary A # 

Methods

arbitrary :: Gen A #

shrink :: A -> [A] #

Arbitrary a => Arbitrary [a] # 

Methods

arbitrary :: Gen [a] #

shrink :: [a] -> [[a]] #

Arbitrary a => Arbitrary (Maybe a) # 

Methods

arbitrary :: Gen (Maybe a) #

shrink :: Maybe a -> [Maybe a] #

Integral a => Arbitrary (Ratio a) # 

Methods

arbitrary :: Gen (Ratio a) #

shrink :: Ratio a -> [Ratio a] #

Arbitrary a => Arbitrary (Identity a) # 

Methods

arbitrary :: Gen (Identity a) #

shrink :: Identity a -> [Identity a] #

HasResolution a => Arbitrary (Fixed a) # 

Methods

arbitrary :: Gen (Fixed a) #

shrink :: Fixed a -> [Fixed a] #

(RealFloat a, Arbitrary a) => Arbitrary (Complex a) # 

Methods

arbitrary :: Gen (Complex a) #

shrink :: Complex a -> [Complex a] #

Arbitrary a => Arbitrary (ZipList a) # 

Methods

arbitrary :: Gen (ZipList a) #

shrink :: ZipList a -> [ZipList a] #

Arbitrary a => Arbitrary (Dual a) # 

Methods

arbitrary :: Gen (Dual a) #

shrink :: Dual a -> [Dual a] #

(Arbitrary a, CoArbitrary a) => Arbitrary (Endo a) # 

Methods

arbitrary :: Gen (Endo a) #

shrink :: Endo a -> [Endo a] #

Arbitrary a => Arbitrary (Sum a) # 

Methods

arbitrary :: Gen (Sum a) #

shrink :: Sum a -> [Sum a] #

Arbitrary a => Arbitrary (Product a) # 

Methods

arbitrary :: Gen (Product a) #

shrink :: Product a -> [Product a] #

Arbitrary a => Arbitrary (First a) # 

Methods

arbitrary :: Gen (First a) #

shrink :: First a -> [First a] #

Arbitrary a => Arbitrary (Last a) # 

Methods

arbitrary :: Gen (Last a) #

shrink :: Last a -> [Last a] #

Arbitrary a => Arbitrary (IntMap a) # 

Methods

arbitrary :: Gen (IntMap a) #

shrink :: IntMap a -> [IntMap a] #

Arbitrary a => Arbitrary (Seq a) # 

Methods

arbitrary :: Gen (Seq a) #

shrink :: Seq a -> [Seq a] #

(Ord a, Arbitrary a) => Arbitrary (Set a) # 

Methods

arbitrary :: Gen (Set a) #

shrink :: Set a -> [Set a] #

Arbitrary a => Arbitrary (Smart a) # 

Methods

arbitrary :: Gen (Smart a) #

shrink :: Smart a -> [Smart a] #

Arbitrary a => Arbitrary (Shrink2 a) # 

Methods

arbitrary :: Gen (Shrink2 a) #

shrink :: Shrink2 a -> [Shrink2 a] #

Integral a => Arbitrary (Small a) # 

Methods

arbitrary :: Gen (Small a) #

shrink :: Small a -> [Small a] #

(Integral a, Bounded a) => Arbitrary (Large a) # 

Methods

arbitrary :: Gen (Large a) #

shrink :: Large a -> [Large a] #

(Num a, Ord a, Arbitrary a) => Arbitrary (NonNegative a) # 
(Num a, Eq a, Arbitrary a) => Arbitrary (NonZero a) # 

Methods

arbitrary :: Gen (NonZero a) #

shrink :: NonZero a -> [NonZero a] #

(Num a, Ord a, Arbitrary a) => Arbitrary (Positive a) # 

Methods

arbitrary :: Gen (Positive a) #

shrink :: Positive a -> [Positive a] #

(Arbitrary a, Ord a) => Arbitrary (SortedList a) # 
Arbitrary a => Arbitrary (InfiniteList a) # 
Arbitrary a => Arbitrary (NonEmptyList a) # 
(Ord a, Arbitrary a) => Arbitrary (OrderedList a) # 
Arbitrary a => Arbitrary (Fixed a) # 

Methods

arbitrary :: Gen (Fixed a) #

shrink :: Fixed a -> [Fixed a] #

Arbitrary a => Arbitrary (Blind a) # 

Methods

arbitrary :: Gen (Blind a) #

shrink :: Blind a -> [Blind a] #

(CoArbitrary a, Arbitrary b) => Arbitrary (a -> b) # 

Methods

arbitrary :: Gen (a -> b) #

shrink :: (a -> b) -> [a -> b] #

(Arbitrary a, Arbitrary b) => Arbitrary (Either a b) # 

Methods

arbitrary :: Gen (Either a b) #

shrink :: Either a b -> [Either a b] #

(Arbitrary a, Arbitrary b) => Arbitrary (a, b) # 

Methods

arbitrary :: Gen (a, b) #

shrink :: (a, b) -> [(a, b)] #

Arbitrary (m a) => Arbitrary (WrappedMonad m a) # 

Methods

arbitrary :: Gen (WrappedMonad m a) #

shrink :: WrappedMonad m a -> [WrappedMonad m a] #

(Ord k, Arbitrary k, Arbitrary v) => Arbitrary (Map k v) # 

Methods

arbitrary :: Gen (Map k v) #

shrink :: Map k v -> [Map k v] #

(Arbitrary a, ShrinkState s a) => Arbitrary (Shrinking s a) # 

Methods

arbitrary :: Gen (Shrinking s a) #

shrink :: Shrinking s a -> [Shrinking s a] #

(Function a, CoArbitrary a, Arbitrary b) => Arbitrary (Fun a b) # 

Methods

arbitrary :: Gen (Fun a b) #

shrink :: Fun a b -> [Fun a b] #

(Function a, CoArbitrary a, Arbitrary b) => Arbitrary ((:->) a b) # 

Methods

arbitrary :: Gen (a :-> b) #

shrink :: (a :-> b) -> [a :-> b] #

(Arbitrary a, Arbitrary b, Arbitrary c) => Arbitrary (a, b, c) # 

Methods

arbitrary :: Gen (a, b, c) #

shrink :: (a, b, c) -> [(a, b, c)] #

Arbitrary (a b c) => Arbitrary (WrappedArrow a b c) # 

Methods

arbitrary :: Gen (WrappedArrow a b c) #

shrink :: WrappedArrow a b c -> [WrappedArrow a b c] #

Arbitrary a => Arbitrary (Const k a b) # 

Methods

arbitrary :: Gen (Const k a b) #

shrink :: Const k a b -> [Const k a b] #

Arbitrary (f a) => Arbitrary (Alt k f a) # 

Methods

arbitrary :: Gen (Alt k f a) #

shrink :: Alt k f a -> [Alt k f a] #

Arbitrary a => Arbitrary (Constant k a b) # 

Methods

arbitrary :: Gen (Constant k a b) #

shrink :: Constant k a b -> [Constant k a b] #

(Arbitrary a, Arbitrary b, Arbitrary c, Arbitrary d) => Arbitrary (a, b, c, d) # 

Methods

arbitrary :: Gen (a, b, c, d) #

shrink :: (a, b, c, d) -> [(a, b, c, d)] #

(Arbitrary1 f, Arbitrary1 g, Arbitrary a) => Arbitrary (Product * f g a) # 

Methods

arbitrary :: Gen (Product * f g a) #

shrink :: Product * f g a -> [Product * f g a] #

(Arbitrary a, Arbitrary b, Arbitrary c, Arbitrary d, Arbitrary e) => Arbitrary (a, b, c, d, e) # 

Methods

arbitrary :: Gen (a, b, c, d, e) #

shrink :: (a, b, c, d, e) -> [(a, b, c, d, e)] #

(Arbitrary1 f, Arbitrary1 g, Arbitrary a) => Arbitrary (Compose * * f g a) # 

Methods

arbitrary :: Gen (Compose * * f g a) #

shrink :: Compose * * f g a -> [Compose * * f g a] #

(Arbitrary a, Arbitrary b, Arbitrary c, Arbitrary d, Arbitrary e, Arbitrary f) => Arbitrary (a, b, c, d, e, f) # 

Methods

arbitrary :: Gen (a, b, c, d, e, f) #

shrink :: (a, b, c, d, e, f) -> [(a, b, c, d, e, f)] #

(Arbitrary a, Arbitrary b, Arbitrary c, Arbitrary d, Arbitrary e, Arbitrary f, Arbitrary g) => Arbitrary (a, b, c, d, e, f, g) # 

Methods

arbitrary :: Gen (a, b, c, d, e, f, g) #

shrink :: (a, b, c, d, e, f, g) -> [(a, b, c, d, e, f, g)] #

(Arbitrary a, Arbitrary b, Arbitrary c, Arbitrary d, Arbitrary e, Arbitrary f, Arbitrary g, Arbitrary h) => Arbitrary (a, b, c, d, e, f, g, h) # 

Methods

arbitrary :: Gen (a, b, c, d, e, f, g, h) #

shrink :: (a, b, c, d, e, f, g, h) -> [(a, b, c, d, e, f, g, h)] #

(Arbitrary a, Arbitrary b, Arbitrary c, Arbitrary d, Arbitrary e, Arbitrary f, Arbitrary g, Arbitrary h, Arbitrary i) => Arbitrary (a, b, c, d, e, f, g, h, i) # 

Methods

arbitrary :: Gen (a, b, c, d, e, f, g, h, i) #

shrink :: (a, b, c, d, e, f, g, h, i) -> [(a, b, c, d, e, f, g, h, i)] #

(Arbitrary a, Arbitrary b, Arbitrary c, Arbitrary d, Arbitrary e, Arbitrary f, Arbitrary g, Arbitrary h, Arbitrary i, Arbitrary j) => Arbitrary (a, b, c, d, e, f, g, h, i, j) # 

Methods

arbitrary :: Gen (a, b, c, d, e, f, g, h, i, j) #

shrink :: (a, b, c, d, e, f, g, h, i, j) -> [(a, b, c, d, e, f, g, h, i, j)] #

class CoArbitrary a where #

Used for random generation of functions. You should consider using Fun instead, which can show the generated functions as strings.

If you are using a recent GHC, there is a default definition of coarbitrary using genericCoarbitrary, so if your type has a Generic instance it's enough to say

instance CoArbitrary MyType

You should only use genericCoarbitrary for data types where equality is structural, i.e. if you can't have two different representations of the same value. An example where it's not safe is sets implemented using binary search trees: the same set can be represented as several different trees. Here you would have to explicitly define coarbitrary s = coarbitrary (toList s).

Methods

coarbitrary :: a -> Gen b -> Gen b #

Used to generate a function of type a -> b. The first argument is a value, the second a generator. You should use variant to perturb the random generator; the goal is that different values for the first argument will lead to different calls to variant. An example will help:

instance CoArbitrary a => CoArbitrary [a] where
  coarbitrary []     = variant 0
  coarbitrary (x:xs) = variant 1 . coarbitrary (x,xs)

coarbitrary :: (Generic a, GCoArbitrary (Rep a)) => a -> Gen b -> Gen b #

Used to generate a function of type a -> b. The first argument is a value, the second a generator. You should use variant to perturb the random generator; the goal is that different values for the first argument will lead to different calls to variant. An example will help:

instance CoArbitrary a => CoArbitrary [a] where
  coarbitrary []     = variant 0
  coarbitrary (x:xs) = variant 1 . coarbitrary (x,xs)

Instances

CoArbitrary Bool # 

Methods

coarbitrary :: Bool -> Gen b -> Gen b #

CoArbitrary Char # 

Methods

coarbitrary :: Char -> Gen b -> Gen b #

CoArbitrary Double # 

Methods

coarbitrary :: Double -> Gen b -> Gen b #

CoArbitrary Float # 

Methods

coarbitrary :: Float -> Gen b -> Gen b #

CoArbitrary Int # 

Methods

coarbitrary :: Int -> Gen b -> Gen b #

CoArbitrary Int8 # 

Methods

coarbitrary :: Int8 -> Gen b -> Gen b #

CoArbitrary Int16 # 

Methods

coarbitrary :: Int16 -> Gen b -> Gen b #

CoArbitrary Int32 # 

Methods

coarbitrary :: Int32 -> Gen b -> Gen b #

CoArbitrary Int64 # 

Methods

coarbitrary :: Int64 -> Gen b -> Gen b #

CoArbitrary Integer # 

Methods

coarbitrary :: Integer -> Gen b -> Gen b #

CoArbitrary Ordering # 

Methods

coarbitrary :: Ordering -> Gen b -> Gen b #

CoArbitrary Word # 

Methods

coarbitrary :: Word -> Gen b -> Gen b #

CoArbitrary Word8 # 

Methods

coarbitrary :: Word8 -> Gen b -> Gen b #

CoArbitrary Word16 # 

Methods

coarbitrary :: Word16 -> Gen b -> Gen b #

CoArbitrary Word32 # 

Methods

coarbitrary :: Word32 -> Gen b -> Gen b #

CoArbitrary Word64 # 

Methods

coarbitrary :: Word64 -> Gen b -> Gen b #

CoArbitrary () # 

Methods

coarbitrary :: () -> Gen b -> Gen b #

CoArbitrary Version # 

Methods

coarbitrary :: Version -> Gen b -> Gen b #

CoArbitrary All # 

Methods

coarbitrary :: All -> Gen b -> Gen b #

CoArbitrary Any # 

Methods

coarbitrary :: Any -> Gen b -> Gen b #

CoArbitrary IntSet # 

Methods

coarbitrary :: IntSet -> Gen b -> Gen b #

CoArbitrary OrdC # 

Methods

coarbitrary :: OrdC -> Gen b -> Gen b #

CoArbitrary OrdB # 

Methods

coarbitrary :: OrdB -> Gen b -> Gen b #

CoArbitrary OrdA # 

Methods

coarbitrary :: OrdA -> Gen b -> Gen b #

CoArbitrary C # 

Methods

coarbitrary :: C -> Gen b -> Gen b #

CoArbitrary B # 

Methods

coarbitrary :: B -> Gen b -> Gen b #

CoArbitrary A # 

Methods

coarbitrary :: A -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary [a] # 

Methods

coarbitrary :: [a] -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (Maybe a) # 

Methods

coarbitrary :: Maybe a -> Gen b -> Gen b #

(Integral a, CoArbitrary a) => CoArbitrary (Ratio a) # 

Methods

coarbitrary :: Ratio a -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (Identity a) # 

Methods

coarbitrary :: Identity a -> Gen b -> Gen b #

HasResolution a => CoArbitrary (Fixed a) # 

Methods

coarbitrary :: Fixed a -> Gen b -> Gen b #

(RealFloat a, CoArbitrary a) => CoArbitrary (Complex a) # 

Methods

coarbitrary :: Complex a -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (ZipList a) # 

Methods

coarbitrary :: ZipList a -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (Dual a) # 

Methods

coarbitrary :: Dual a -> Gen b -> Gen b #

(Arbitrary a, CoArbitrary a) => CoArbitrary (Endo a) # 

Methods

coarbitrary :: Endo a -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (Sum a) # 

Methods

coarbitrary :: Sum a -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (Product a) # 

Methods

coarbitrary :: Product a -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (First a) # 

Methods

coarbitrary :: First a -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (Last a) # 

Methods

coarbitrary :: Last a -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (IntMap a) # 

Methods

coarbitrary :: IntMap a -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (Seq a) # 

Methods

coarbitrary :: Seq a -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (Set a) # 

Methods

coarbitrary :: Set a -> Gen b -> Gen b #

(Arbitrary a, CoArbitrary b) => CoArbitrary (a -> b) # 

Methods

coarbitrary :: (a -> b) -> Gen b -> Gen b #

(CoArbitrary a, CoArbitrary b) => CoArbitrary (Either a b) # 

Methods

coarbitrary :: Either a b -> Gen b -> Gen b #

(CoArbitrary a, CoArbitrary b) => CoArbitrary (a, b) # 

Methods

coarbitrary :: (a, b) -> Gen b -> Gen b #

(CoArbitrary k, CoArbitrary v) => CoArbitrary (Map k v) # 

Methods

coarbitrary :: Map k v -> Gen b -> Gen b #

(CoArbitrary a, CoArbitrary b, CoArbitrary c) => CoArbitrary (a, b, c) # 

Methods

coarbitrary :: (a, b, c) -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (Const k a b) # 

Methods

coarbitrary :: Const k a b -> Gen b -> Gen b #

CoArbitrary (f a) => CoArbitrary (Alt k f a) # 

Methods

coarbitrary :: Alt k f a -> Gen b -> Gen b #

CoArbitrary a => CoArbitrary (Constant k a b) # 

Methods

coarbitrary :: Constant k a b -> Gen b -> Gen b #

(CoArbitrary a, CoArbitrary b, CoArbitrary c, CoArbitrary d) => CoArbitrary (a, b, c, d) # 

Methods

coarbitrary :: (a, b, c, d) -> Gen b -> Gen b #

(CoArbitrary a, CoArbitrary b, CoArbitrary c, CoArbitrary d, CoArbitrary e) => CoArbitrary (a, b, c, d, e) # 

Methods

coarbitrary :: (a, b, c, d, e) -> Gen b -> Gen b #

Unary and Binary classes

class Arbitrary1 f where #

Lifting of the Arbitrary class to unary type constructors.

Minimal complete definition

liftArbitrary

Methods

liftArbitrary :: Gen a -> Gen (f a) #

liftShrink :: (a -> [a]) -> f a -> [f a] #

Instances

Arbitrary1 [] # 

Methods

liftArbitrary :: Gen a -> Gen [a] #

liftShrink :: (a -> [a]) -> [a] -> [[a]] #

Arbitrary1 Maybe # 

Methods

liftArbitrary :: Gen a -> Gen (Maybe a) #

liftShrink :: (a -> [a]) -> Maybe a -> [Maybe a] #

Arbitrary1 Identity # 

Methods

liftArbitrary :: Gen a -> Gen (Identity a) #

liftShrink :: (a -> [a]) -> Identity a -> [Identity a] #

Arbitrary1 ZipList # 

Methods

liftArbitrary :: Gen a -> Gen (ZipList a) #

liftShrink :: (a -> [a]) -> ZipList a -> [ZipList a] #

Arbitrary1 IntMap # 

Methods

liftArbitrary :: Gen a -> Gen (IntMap a) #

liftShrink :: (a -> [a]) -> IntMap a -> [IntMap a] #

Arbitrary1 Seq # 

Methods

liftArbitrary :: Gen a -> Gen (Seq a) #

liftShrink :: (a -> [a]) -> Seq a -> [Seq a] #

CoArbitrary a => Arbitrary1 ((->) a) # 

Methods

liftArbitrary :: Gen a -> Gen (a -> a) #

liftShrink :: (a -> [a]) -> (a -> a) -> [a -> a] #

Arbitrary a => Arbitrary1 (Either a) # 

Methods

liftArbitrary :: Gen a -> Gen (Either a a) #

liftShrink :: (a -> [a]) -> Either a a -> [Either a a] #

Arbitrary a => Arbitrary1 ((,) a) # 

Methods

liftArbitrary :: Gen a -> Gen (a, a) #

liftShrink :: (a -> [a]) -> (a, a) -> [(a, a)] #

(Ord k, Arbitrary k) => Arbitrary1 (Map k) # 

Methods

liftArbitrary :: Gen a -> Gen (Map k a) #

liftShrink :: (a -> [a]) -> Map k a -> [Map k a] #

Arbitrary a => Arbitrary1 (Const * a) # 

Methods

liftArbitrary :: Gen a -> Gen (Const * a a) #

liftShrink :: (a -> [a]) -> Const * a a -> [Const * a a] #

Arbitrary a => Arbitrary1 (Constant * a) # 

Methods

liftArbitrary :: Gen a -> Gen (Constant * a a) #

liftShrink :: (a -> [a]) -> Constant * a a -> [Constant * a a] #

(Arbitrary1 f, Arbitrary1 g) => Arbitrary1 (Product * f g) # 

Methods

liftArbitrary :: Gen a -> Gen (Product * f g a) #

liftShrink :: (a -> [a]) -> Product * f g a -> [Product * f g a] #

(Arbitrary1 f, Arbitrary1 g) => Arbitrary1 (Compose * * f g) # 

Methods

liftArbitrary :: Gen a -> Gen (Compose * * f g a) #

liftShrink :: (a -> [a]) -> Compose * * f g a -> [Compose * * f g a] #

arbitrary1 :: (Arbitrary1 f, Arbitrary a) => Gen (f a) #

shrink1 :: (Arbitrary1 f, Arbitrary a) => f a -> [f a] #

class Arbitrary2 f where #

Lifting of the Arbitrary class to binary type constructors.

Minimal complete definition

liftArbitrary2

Methods

liftArbitrary2 :: Gen a -> Gen b -> Gen (f a b) #

liftShrink2 :: (a -> [a]) -> (b -> [b]) -> f a b -> [f a b] #

Instances

Arbitrary2 Either # 

Methods

liftArbitrary2 :: Gen a -> Gen b -> Gen (Either a b) #

liftShrink2 :: (a -> [a]) -> (b -> [b]) -> Either a b -> [Either a b] #

Arbitrary2 (,) # 

Methods

liftArbitrary2 :: Gen a -> Gen b -> Gen (a, b) #

liftShrink2 :: (a -> [a]) -> (b -> [b]) -> (a, b) -> [(a, b)] #

Arbitrary2 (Const *) # 

Methods

liftArbitrary2 :: Gen a -> Gen b -> Gen (Const * a b) #

liftShrink2 :: (a -> [a]) -> (b -> [b]) -> Const * a b -> [Const * a b] #

Arbitrary2 (Constant *) # 

Methods

liftArbitrary2 :: Gen a -> Gen b -> Gen (Constant * a b) #

liftShrink2 :: (a -> [a]) -> (b -> [b]) -> Constant * a b -> [Constant * a b] #

arbitrary2 :: (Arbitrary2 f, Arbitrary a, Arbitrary b) => Gen (f a b) #

shrink2 :: (Arbitrary2 f, Arbitrary a, Arbitrary b) => f a b -> [f a b] #

Helper functions for implementing arbitrary

applyArbitrary2 :: (Arbitrary a, Arbitrary b) => (a -> b -> r) -> Gen r #

Apply a binary function to random arguments.

applyArbitrary3 :: (Arbitrary a, Arbitrary b, Arbitrary c) => (a -> b -> c -> r) -> Gen r #

Apply a ternary function to random arguments.

applyArbitrary4 :: (Arbitrary a, Arbitrary b, Arbitrary c, Arbitrary d) => (a -> b -> c -> d -> r) -> Gen r #

Apply a function of arity 4 to random arguments.

arbitrarySizedIntegral :: Integral a => Gen a #

Generates an integral number. The number can be positive or negative and its maximum absolute value depends on the size parameter.

arbitrarySizedNatural :: Integral a => Gen a #

Generates a natural number. The number's maximum value depends on the size parameter.

arbitraryBoundedIntegral :: (Bounded a, Integral a) => Gen a #

Generates an integral number. The number is chosen uniformly from the entire range of the type. You may want to use arbitrarySizedBoundedIntegral instead.

arbitrarySizedBoundedIntegral :: (Bounded a, Integral a) => Gen a #

Generates an integral number from a bounded domain. The number is chosen from the entire range of the type, but small numbers are generated more often than big numbers. Inspired by demands from Phil Wadler.

arbitrarySizedFractional :: Fractional a => Gen a #

Generates a fractional number. The number can be positive or negative and its maximum absolute value depends on the size parameter.

arbitraryBoundedRandom :: (Bounded a, Random a) => Gen a #

Generates an element of a bounded type. The element is chosen from the entire range of the type.

arbitraryBoundedEnum :: (Bounded a, Enum a) => Gen a #

Generates an element of a bounded enumeration.

Generators for various kinds of character

arbitraryUnicodeChar :: Gen Char #

Generates any Unicode character (but not a surrogate)

arbitraryASCIIChar :: Gen Char #

Generates a random ASCII character (0-127).

arbitraryPrintableChar :: Gen Char #

Generates a printable Unicode character.

Helper functions for implementing shrink

genericShrink :: (Generic a, RecursivelyShrink (Rep a), GSubterms (Rep a) a) => a -> [a] #

Shrink a term to any of its immediate subterms, and also recursively shrink all subterms.

subterms :: (Generic a, GSubterms (Rep a) a) => a -> [a] #

All immediate subterms of a term.

recursivelyShrink :: (Generic a, RecursivelyShrink (Rep a)) => a -> [a] #

Recursively shrink all immediate subterms.

genericCoarbitrary :: (Generic a, GCoArbitrary (Rep a)) => a -> Gen b -> Gen b #

Generic CoArbitrary implementation.

shrinkNothing :: a -> [a] #

Returns no shrinking alternatives.

shrinkList :: (a -> [a]) -> [a] -> [[a]] #

Shrink a list of values given a shrinking function for individual values.

shrinkMap :: Arbitrary a => (a -> b) -> (b -> a) -> b -> [b] #

Map a shrink function to another domain. This is handy if your data type has special invariants, but is almost isomorphic to some other type.

shrinkOrderedList :: (Ord a, Arbitrary a) => [a] -> [[a]]
shrinkOrderedList = shrinkMap sort id

shrinkSet :: (Ord a, Arbitrary a) => Set a -> Set [a]
shrinkSet = shrinkMap fromList toList

shrinkMapBy :: (a -> b) -> (b -> a) -> (a -> [a]) -> b -> [b] #

Non-overloaded version of shrinkMap.

shrinkIntegral :: Integral a => a -> [a] #

Shrink an integral number.

shrinkRealFrac :: RealFrac a => a -> [a] #

Shrink a fraction, preferring numbers with smaller numerators or denominators. See also shrinkDecimal.

shrinkDecimal :: RealFrac a => a -> [a] #

Shrink a real number, preferring numbers with shorter decimal representations. See also shrinkRealFrac.

Helper functions for implementing coarbitrary

coarbitraryIntegral :: Integral a => a -> Gen b -> Gen b #

A coarbitrary implementation for integral numbers.

coarbitraryReal :: Real a => a -> Gen b -> Gen b #

A coarbitrary implementation for real numbers.

coarbitraryShow :: Show a => a -> Gen b -> Gen b #

coarbitrary helper for lazy people :-).

coarbitraryEnum :: Enum a => a -> Gen b -> Gen b #

A coarbitrary implementation for enums.

(><) :: (Gen a -> Gen a) -> (Gen a -> Gen a) -> Gen a -> Gen a #

Deprecated: Use ordinary function composition instead

Combine two generator perturbing functions, for example the results of calls to variant or coarbitrary.

Generators which use arbitrary

vector :: Arbitrary a => Int -> Gen [a] #

Generates a list of a given length.

orderedList :: (Ord a, Arbitrary a) => Gen [a] #

Generates an ordered list.

infiniteList :: Arbitrary a => Gen [a] #

Generates an infinite list.