nonempty-wrapper-quickcheck-0.1.0.0: QuickCheck instance for 'NonEmpty'
CopyrightGautier DI FOLCO
LicenseBSD2
MaintainerGautier DI FOLCO <gautier.difolco@gmail.com>
StabilityUnstable
PortabilityGHC
Safe HaskellNone
LanguageHaskell2010

Test.QuickCheck.Instances.NonEmpty

Description

QuickCheck's Arbitrary instance for NonEmpty.

Synopsis

Documentation

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

Instances details
Arbitrary Bool 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen Bool #

shrink :: Bool -> [Bool] #

Arbitrary Char 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen Char #

shrink :: Char -> [Char] #

Arbitrary Double 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Float 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen Float #

shrink :: Float -> [Float] #

Arbitrary Int 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen Int #

shrink :: Int -> [Int] #

Arbitrary Int8 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen Int8 #

shrink :: Int8 -> [Int8] #

Arbitrary Int16 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen Int16 #

shrink :: Int16 -> [Int16] #

Arbitrary Int32 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen Int32 #

shrink :: Int32 -> [Int32] #

Arbitrary Int64 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen Int64 #

shrink :: Int64 -> [Int64] #

Arbitrary Integer 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Ordering 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Word 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen Word #

shrink :: Word -> [Word] #

Arbitrary Word8 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen Word8 #

shrink :: Word8 -> [Word8] #

Arbitrary Word16 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Word32 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Word64 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary () 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen () #

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

Arbitrary Version

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

Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary QCGen 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen QCGen #

shrink :: QCGen -> [QCGen] #

Arbitrary ASCIIString 
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary UnicodeString 
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary PrintableString 
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary ExitCode 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary All 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen All #

shrink :: All -> [All] #

Arbitrary Any 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen Any #

shrink :: Any -> [Any] #

Arbitrary CChar 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen CChar #

shrink :: CChar -> [CChar] #

Arbitrary CSChar 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CUChar 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CShort 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CUShort 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CInt 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen CInt #

shrink :: CInt -> [CInt] #

Arbitrary CUInt 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen CUInt #

shrink :: CUInt -> [CUInt] #

Arbitrary CLong 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen CLong #

shrink :: CLong -> [CLong] #

Arbitrary CULong 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CLLong 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CULLong 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CFloat 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CDouble 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CPtrdiff 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CSize 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen CSize #

shrink :: CSize -> [CSize] #

Arbitrary CWchar 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CSigAtomic 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CClock 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CTime 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen CTime #

shrink :: CTime -> [CTime] #

Arbitrary CUSeconds 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CSUSeconds 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CIntPtr 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CUIntPtr 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CIntMax 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CUIntMax 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary IntSet 
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary [a] 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen [a] #

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

Arbitrary a => Arbitrary (Maybe a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Maybe a) #

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

Integral a => Arbitrary (Ratio a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Ratio a) #

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

Arbitrary a => Arbitrary (Blind a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Methods

arbitrary :: Gen (Blind a) #

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

Arbitrary a => Arbitrary (Fixed a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Methods

arbitrary :: Gen (Fixed a) #

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

(Ord a, Arbitrary a) => Arbitrary (OrderedList a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary a => Arbitrary (NonEmptyList a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary a => Arbitrary (InfiniteList a) 
Instance details

Defined in Test.QuickCheck.Modifiers

(Arbitrary a, Ord a) => Arbitrary (SortedList a) 
Instance details

Defined in Test.QuickCheck.Modifiers

(Num a, Ord a, Arbitrary a) => Arbitrary (Positive a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Methods

arbitrary :: Gen (Positive a) #

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

(Num a, Ord a, Arbitrary a) => Arbitrary (Negative a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Methods

arbitrary :: Gen (Negative a) #

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

(Num a, Eq a, Arbitrary a) => Arbitrary (NonZero a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Methods

arbitrary :: Gen (NonZero a) #

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

(Num a, Ord a, Arbitrary a) => Arbitrary (NonNegative a) 
Instance details

Defined in Test.QuickCheck.Modifiers

(Num a, Ord a, Arbitrary a) => Arbitrary (NonPositive a) 
Instance details

Defined in Test.QuickCheck.Modifiers

(Integral a, Bounded a) => Arbitrary (Large a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Methods

arbitrary :: Gen (Large a) #

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

Integral a => Arbitrary (Small a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Methods

arbitrary :: Gen (Small a) #

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

Arbitrary a => Arbitrary (Shrink2 a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Methods

arbitrary :: Gen (Shrink2 a) #

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

Arbitrary a => Arbitrary (Smart a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Methods

arbitrary :: Gen (Smart a) #

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

Arbitrary a => Arbitrary (Complex a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Complex a) #

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

Arbitrary a => Arbitrary (ZipList a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (ZipList a) #

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

Arbitrary a => Arbitrary (Identity a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Identity a) #

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

Arbitrary a => Arbitrary (First a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (First a) #

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

Arbitrary a => Arbitrary (Last a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Last a) #

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

Arbitrary a => Arbitrary (Dual a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Dual a) #

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

(Arbitrary a, CoArbitrary a) => Arbitrary (Endo a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Endo a) #

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

Arbitrary a => Arbitrary (Sum a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Sum a) #

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

Arbitrary a => Arbitrary (Product a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Product a) #

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

Arbitrary a => Arbitrary (IntMap a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (IntMap a) #

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

Arbitrary a => Arbitrary (Tree a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Tree a) #

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

Arbitrary a => Arbitrary (Seq a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Seq a) #

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

(Ord a, Arbitrary a) => Arbitrary (Set a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Set a) #

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

(Arbitrary a, Semigroup a, NonEmptySingleton a, NonEmptyFromContainer a, Arbitrary (NonEmptySingletonElement a)) => Arbitrary (NonEmpty a) Source # 
Instance details

Defined in Test.QuickCheck.Instances.NonEmpty

Methods

arbitrary :: Gen (NonEmpty a) #

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

Arbitrary a => Arbitrary (InfiniteListInternalData a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Methods

arbitrary :: Gen (InfiniteListInternalData a) #

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

(CoArbitrary a, Arbitrary b) => Arbitrary (a -> b) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (a -> b) #

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

(Arbitrary a, Arbitrary b) => Arbitrary (Either a b) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Either a b) #

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

(Arbitrary a, Arbitrary b) => Arbitrary (a, b) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (a, b) #

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

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

Defined in Test.QuickCheck.Function

Methods

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

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

(Function a, CoArbitrary a, Arbitrary b) => Arbitrary (Fun a b) 
Instance details

Defined in Test.QuickCheck.Function

Methods

arbitrary :: Gen (Fun a b) #

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

(Arbitrary a, ShrinkState s a) => Arbitrary (Shrinking s a) 
Instance details

Defined in Test.QuickCheck.Modifiers

Methods

arbitrary :: Gen (Shrinking s a) #

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

HasResolution a => Arbitrary (Fixed a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Fixed a) #

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

Arbitrary (m a) => Arbitrary (WrappedMonad m a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (WrappedMonad m a) #

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

(Ord k, Arbitrary k, Arbitrary v) => Arbitrary (Map k v) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Map k v) #

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

(Arbitrary a, Arbitrary b, Arbitrary c) => Arbitrary (a, b, c) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

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

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

Arbitrary (a b c) => Arbitrary (WrappedArrow a b c) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (WrappedArrow a b c) #

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

Arbitrary a => Arbitrary (Const a b) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Const a b) #

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

Arbitrary (f a) => Arbitrary (Alt f a) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Alt f a) #

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

Arbitrary a => Arbitrary (Constant a b) 
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (Constant a b) #

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

(Arbitrary a, Arbitrary b, Arbitrary c, Arbitrary d) => Arbitrary (a, b, c, d) 
Instance details

Defined in Test.QuickCheck.Arbitrary

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) 
Instance details

Defined in Test.QuickCheck.Arbitrary

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) 
Instance details

Defined in Test.QuickCheck.Arbitrary

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) 
Instance details

Defined in Test.QuickCheck.Arbitrary

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) 
Instance details

Defined in Test.QuickCheck.Arbitrary

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) 
Instance details

Defined in Test.QuickCheck.Arbitrary

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) 
Instance details

Defined in Test.QuickCheck.Arbitrary

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) 
Instance details

Defined in Test.QuickCheck.Arbitrary

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) 
Instance details

Defined in Test.QuickCheck.Arbitrary

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)] #

Orphan instances