QuickCheck-2.15: Automatic testing of Haskell programs

Safe Haskell | Safe
Language | Haskell2010

Test.QuickCheck

Contents

- Running tests
  - Running tests verbosely
  - Testing all properties in a module
  - Testing polymorphic properties
- The `Arbitrary` typeclass: generation of random values
  - Helper functions for implementing `shrink`
  - Lifting of `Arbitrary` to unary and binary type constructors
- The `Gen` monad: combinators for building random generators
  - Generator combinators
  - Generators for lists
  - Generators for particular types
  - Running generators
  - Debugging generators
- The `Function` typeclass: generation of random shrinkable, showable functions
- The `CoArbitrary` typeclass: generation of functions the old-fashioned way
- Type-level modifiers for changing generator behavior
- Property combinators
  - Controlling property execution
  - Conjunction and disjunction
  - What to do on failure
- Analysing test case distribution
  - Checking test case distribution
  - Generating example test cases

Description

The QuickCheck manual gives detailed information about using QuickCheck effectively. You can also try https://begriffs.com/posts/2017-01-14-design-use-quickcheck.html, a tutorial written by a user of QuickCheck.

To start using QuickCheck, write down your property as a function returning `Bool`. For example, to check that reversing a list twice gives back the same list you can write:

    import Test.QuickCheck

    prop_reverse :: [Int] -> Bool
    prop_reverse xs = reverse (reverse xs) == xs

You can then use QuickCheck to test `prop_reverse` on 100 random lists:

    >>> quickCheck prop_reverse
    +++ OK, passed 100 tests.

To run more tests you can use the `withMaxSuccess` combinator:

    >>> quickCheck (withMaxSuccess 10000 prop_reverse)
    +++ OK, passed 10000 tests.

To use QuickCheck on your own data types you will need to write `Arbitrary` instances for those types. See the QuickCheck manual for details about how to do that.

When testing fails `quickCheck` will try to give you a minimal counterexample to your property: @ import Test.QuickCheck

prop_reverse_bad :: [Int] -> Bool prop_reverse_bad xs = reverse xs == xs

    >>> quickCheck prop_reverse_bad
    *** Failed! Falsified (after 3 tests and 3 shrinks):
    [0,1]
    @

However, beware because not all properties that ought to fail will fail when you expect them to:

    >>> quickCheck $  x y -> x == y
    +++ Ok, passed 100 tests.

That's because GHCi will default any type variables in your property to `()`, so in the example above `quickCheck` was really testing that `()` is equal to itself. To avoid this behaviour it is best practise to monomorphise your polymorphic properties when testing:

    >>> quickCheck $  x y -> (x :: Int) == y
    *** Failed! Falsified (after 4 tests and 3 shrinks):
    0
    1

Synopsis

- quickCheck :: Testable prop => prop -> IO ()
- data Args = Args {
  - replay :: Maybe (QCGen, Int)
  - maxSuccess :: Int
  - maxDiscardRatio :: Int
  - maxSize :: Int
  - chatty :: Bool
  - maxShrinks :: Int
  }
- data Result
  - = Success {
    - numTests :: Int
    - numDiscarded :: Int
    - labels :: !(Map [String] Int)
    - classes :: !(Map String Int)
    - tables :: !(Map String (Map String Int))
    - output :: String
    }
  - | GaveUp {
    - numTests :: Int
    - numDiscarded :: Int
    - labels :: !(Map [String] Int)
    - classes :: !(Map String Int)
    - tables :: !(Map String (Map String Int))
    - output :: String
    }
  - | Failure {
    - numTests :: Int
    - numDiscarded :: Int
    - numShrinks :: Int
    - numShrinkTries :: Int
    - numShrinkFinal :: Int
    - usedSeed :: QCGen
    - usedSize :: Int
    - reason :: String
    - theException :: Maybe AnException
    - output :: String
    - failingTestCase :: [String]
    - failingLabels :: [String]
    - failingClasses :: Set String
    - witnesses :: [Witness]
    }
  - | NoExpectedFailure {
    - numTests :: Int
    - numDiscarded :: Int
    - labels :: !(Map [String] Int)
    - classes :: !(Map String Int)
    - tables :: !(Map String (Map String Int))
    - output :: String
    }
- stdArgs :: Args
- quickCheckWith :: Testable prop => Args -> prop -> IO ()
- quickCheckWithResult :: Testable prop => Args -> prop -> IO Result
- quickCheckResult :: Testable prop => prop -> IO Result
- recheck :: Testable prop => Result -> prop -> IO ()
- isSuccess :: Result -> Bool
- verboseCheck :: Testable prop => prop -> IO ()
- verboseCheckWith :: Testable prop => Args -> prop -> IO ()
- verboseCheckWithResult :: Testable prop => Args -> prop -> IO Result
- verboseCheckResult :: Testable prop => prop -> IO Result
- quickCheckAll :: Q Exp
- verboseCheckAll :: Q Exp
- forAllProperties :: Q Exp
- allProperties :: Q Exp
- polyQuickCheck :: Name -> ExpQ
- polyVerboseCheck :: Name -> ExpQ
- monomorphic :: Name -> ExpQ
- class Arbitrary a where
  - arbitrary :: Gen a
  - shrink :: a -> [a]
- genericShrink :: (Generic a, RecursivelyShrink (Rep a), GSubterms (Rep a) a) => a -> [a]
- subterms :: (Generic a, GSubterms (Rep a) a) => a -> [a]
- recursivelyShrink :: (Generic a, RecursivelyShrink (Rep a)) => a -> [a]
- shrinkNothing :: a -> [a]
- shrinkList :: (a -> [a]) -> [a] -> [[a]]
- shrinkMap :: Arbitrary a => (a -> b) -> (b -> a) -> b -> [b]
- shrinkMapBy :: (a -> b) -> (b -> a) -> (a -> [a]) -> b -> [b]
- shrinkIntegral :: Integral a => a -> [a]
- shrinkRealFrac :: RealFrac a => a -> [a]
- shrinkBoundedEnum :: (Bounded a, Enum a, Eq a) => a -> [a]
- shrinkDecimal :: RealFrac a => a -> [a]
- class Arbitrary1 (f :: Type -> Type) where
  - liftArbitrary :: Gen a -> Gen (f a)
  - liftShrink :: (a -> [a]) -> f a -> [f a]
- arbitrary1 :: (Arbitrary1 f, Arbitrary a) => Gen (f a)
- shrink1 :: (Arbitrary1 f, Arbitrary a) => f a -> [f a]
- class Arbitrary2 (f :: Type -> Type -> Type) where
  - liftArbitrary2 :: Gen a -> Gen b -> Gen (f a b)
  - liftShrink2 :: (a -> [a]) -> (b -> [b]) -> f a b -> [f 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]
- data Gen a
- choose :: Random a => (a, a) -> Gen a
- chooseInt :: (Int, Int) -> Gen Int
- chooseInteger :: (Integer, Integer) -> Gen Integer
- chooseBoundedIntegral :: (Bounded a, Integral a) => (a, a) -> Gen a
- chooseEnum :: Enum a => (a, a) -> Gen a
- chooseAny :: Random a => Gen a
- oneof :: HasCallStack => [Gen a] -> Gen a
- frequency :: HasCallStack => [(Int, Gen a)] -> Gen a
- elements :: HasCallStack => [a] -> Gen a
- growingElements :: HasCallStack => [a] -> Gen a
- sized :: (Int -> Gen a) -> Gen a
- getSize :: Gen Int
- resize :: HasCallStack => Int -> Gen a -> Gen a
- scale :: (Int -> Int) -> Gen a -> Gen a
- suchThat :: Gen a -> (a -> Bool) -> Gen a
- suchThatMap :: Gen a -> (a -> Maybe b) -> Gen b
- suchThatMaybe :: Gen a -> (a -> Bool) -> Gen (Maybe a)
- applyArbitrary2 :: (Arbitrary a, Arbitrary b) => (a -> b -> r) -> Gen r
- applyArbitrary3 :: (Arbitrary a, Arbitrary b, Arbitrary c) => (a -> b -> c -> r) -> Gen r
- applyArbitrary4 :: (Arbitrary a, Arbitrary b, Arbitrary c, Arbitrary d) => (a -> b -> c -> d -> r) -> Gen r
- listOf :: Gen a -> Gen [a]
- listOf1 :: Gen a -> Gen [a]
- vectorOf :: Int -> Gen a -> Gen [a]
- vector :: Arbitrary a => Int -> Gen [a]
- infiniteListOf :: Gen a -> Gen [a]
- infiniteList :: Arbitrary a => Gen [a]
- shuffle :: [a] -> Gen [a]
- sublistOf :: [a] -> Gen [a]
- orderedList :: (Ord a, Arbitrary a) => Gen [a]
- arbitrarySizedIntegral :: Integral a => Gen a
- arbitrarySizedNatural :: Integral a => Gen a
- arbitrarySizedFractional :: Fractional a => Gen a
- arbitrarySizedBoundedIntegral :: (Bounded a, Integral a) => Gen a
- arbitraryBoundedIntegral :: (Bounded a, Integral a) => Gen a
- arbitraryBoundedRandom :: (Bounded a, Random a) => Gen a
- arbitraryBoundedEnum :: (Bounded a, Enum a) => Gen a
- arbitraryUnicodeChar :: Gen Char
- arbitraryASCIIChar :: Gen Char
- arbitraryPrintableChar :: Gen Char
- generate :: Gen a -> IO a
- sample :: Show a => Gen a -> IO ()
- sample' :: Gen a -> IO [a]
- data Fun a b = Fun (a :-> b, b, Shrunk) (a -> b)
- applyFun :: Fun a b -> a -> b
- applyFun2 :: Fun (a, b) c -> a -> b -> c
- applyFun3 :: Fun (a, b, c) d -> a -> b -> c -> d
- pattern Fn :: (a -> b) -> Fun a b
- pattern Fn2 :: (a -> b -> c) -> Fun (a, b) c
- pattern Fn3 :: (a -> b -> c -> d) -> Fun (a, b, c) d
- class Function a where
  - function :: (a -> b) -> a :-> b
- functionMap :: Function b => (a -> b) -> (b -> a) -> (a -> c) -> a :-> c
- functionShow :: (Show a, Read a) => (a -> c) -> a :-> c
- functionIntegral :: Integral a => (a -> b) -> a :-> b
- functionRealFrac :: RealFrac a => (a -> b) -> a :-> b
- functionBoundedEnum :: (Eq a, Bounded a, Enum a) => (a -> b) -> a :-> b
- functionVoid :: (forall b. void -> b) -> void :-> c
- class CoArbitrary a where
  - coarbitrary :: a -> Gen b -> Gen b
- genericCoarbitrary :: (Generic a, GCoArbitrary (Rep a)) => a -> Gen b -> Gen b
- variant :: Integral n => n -> Gen a -> Gen a
- coarbitraryIntegral :: Integral a => a -> Gen b -> Gen b
- coarbitraryReal :: Real a => a -> Gen b -> Gen b
- coarbitraryShow :: Show a => a -> Gen b -> Gen b
- coarbitraryEnum :: Enum a => a -> Gen b -> Gen b
- (><) :: (Gen a -> Gen a) -> (Gen a -> Gen a) -> Gen a -> Gen a
- newtype Blind a = Blind {
  - getBlind :: a
  }
- newtype Fixed a = Fixed {
  - getFixed :: a
  }
- newtype OrderedList a = Ordered {
  - getOrdered :: [a]
  }
- newtype NonEmptyList a = NonEmpty {
  - getNonEmpty :: [a]
  }
- data InfiniteList a = InfiniteList {
  - getInfiniteList :: [a]
  - infiniteListInternalData :: InfiniteListInternalData a
  }
- newtype SortedList a = Sorted {
  - getSorted :: [a]
  }
- newtype Positive a = Positive {
  - getPositive :: a
  }
- newtype Negative a = Negative {
  - getNegative :: a
  }
- newtype NonZero a = NonZero {
  - getNonZero :: a
  }
- newtype NonNegative a = NonNegative {
  - getNonNegative :: a
  }
- newtype NonPositive a = NonPositive {
  - getNonPositive :: a
  }
- newtype Large a = Large {
  - getLarge :: a
  }
- newtype Small a = Small {
  - getSmall :: a
  }
- data Smart a = Smart Int a
- newtype Shrink2 a = Shrink2 {
  - getShrink2 :: a
  }
- data Shrinking s a = Shrinking s a
- class ShrinkState s a where
  - shrinkInit :: a -> s
  - shrinkState :: a -> s -> [(a, s)]
- newtype ASCIIString = ASCIIString {
  - getASCIIString :: String
  }
- newtype UnicodeString = UnicodeString {
  - getUnicodeString :: String
  }
- newtype PrintableString = PrintableString {
  - getPrintableString :: String
  }
- data Property
- class Testable prop where
  - property :: prop -> Property
  - propertyForAllShrinkShow :: Gen a -> (a -> [a]) -> (a -> [String]) -> (a -> prop) -> Property
- forAll :: (Show a, Testable prop) => Gen a -> (a -> prop) -> Property
- forAllShrink :: (Show a, Testable prop) => Gen a -> (a -> [a]) -> (a -> prop) -> Property
- forAllShow :: Testable prop => Gen a -> (a -> String) -> (a -> prop) -> Property
- forAllShrinkShow :: Testable prop => Gen a -> (a -> [a]) -> (a -> String) -> (a -> prop) -> Property
- forAllBlind :: Testable prop => Gen a -> (a -> prop) -> Property
- forAllShrinkBlind :: Testable prop => Gen a -> (a -> [a]) -> (a -> prop) -> Property
- shrinking :: Testable prop => (a -> [a]) -> a -> (a -> prop) -> Property
- (==>) :: Testable prop => Bool -> prop -> Property
- data Discard = Discard
- discard :: a
- (===) :: (Eq a, Show a) => a -> a -> Property
- (=/=) :: (Eq a, Show a) => a -> a -> Property
- total :: NFData a => a -> Property
- ioProperty :: Testable prop => IO prop -> Property
- idempotentIOProperty :: Testable prop => IO prop -> Property
- verbose :: Testable prop => prop -> Property
- verboseShrinking :: Testable prop => prop -> Property
- noShrinking :: Testable prop => prop -> Property
- withMaxSuccess :: Testable prop => Int -> prop -> Property
- within :: Testable prop => Int -> prop -> Property
- discardAfter :: Testable prop => Int -> prop -> Property
- withDiscardRatio :: Testable prop => Int -> prop -> Property
- withMaxSize :: Testable prop => Int -> prop -> Property
- withMaxShrinks :: Testable prop => Int -> prop -> Property
- once :: Testable prop => prop -> Property
- again :: Testable prop => prop -> Property
- mapSize :: Testable prop => (Int -> Int) -> prop -> Property
- (.&.) :: (Testable prop1, Testable prop2) => prop1 -> prop2 -> Property
- (.&&.) :: (Testable prop1, Testable prop2) => prop1 -> prop2 -> Property
- conjoin :: Testable prop => [prop] -> Property
- (.||.) :: (Testable prop1, Testable prop2) => prop1 -> prop2 -> Property
- disjoin :: Testable prop => [prop] -> Property
- data Witness = (Typeable a, Show a) => Wit a
- witness :: (Typeable a, Show a, Testable prop) => a -> prop -> Property
- coerceWitness :: Typeable a => Witness -> a
- castWitness :: Typeable a => Witness -> Maybe a
- counterexample :: Testable prop => String -> prop -> Property
- printTestCase :: Testable prop => String -> prop -> Property
- whenFail :: Testable prop => IO () -> prop -> Property
- whenFail' :: Testable prop => IO () -> prop -> Property
- expectFailure :: Testable prop => prop -> Property
- label :: Testable prop => String -> prop -> Property
- collect :: (Show a, Testable prop) => a -> prop -> Property
- classify :: Testable prop => Bool -> String -> prop -> Property
- tabulate :: Testable prop => String -> [String] -> prop -> Property
- cover :: Testable prop => Double -> Bool -> String -> prop -> Property
- coverTable :: Testable prop => String -> [(String, Double)] -> prop -> Property
- checkCoverage :: Testable prop => prop -> Property
- checkCoverageWith :: Testable prop => Confidence -> prop -> Property
- data Confidence = Confidence {
  - certainty :: Integer
  - tolerance :: Double
  }
- stdConfidence :: Confidence
- labelledExamples :: Testable prop => prop -> IO ()
- labelledExamplesWith :: Testable prop => Args -> prop -> IO ()
- labelledExamplesWithResult :: Testable prop => Args -> prop -> IO Result
- labelledExamplesResult :: Testable prop => prop -> IO Result

# Running tests

quickCheck :: Testable prop => prop -> IO () #

Tests a property and prints the results to `stdout`.

By default up to 100 tests are performed, which may not be enough to find all bugs. To run more tests, use `withMaxSuccess`.

If you want to get the counterexample as a Haskell value, rather than just printing it, try the quickcheck-with-counterexamples package.

data Args #

Args specifies arguments to the QuickCheck driver

Constructors

Args |

Fields

- replay :: Maybe (QCGen, Int)

  Should we replay a previous test? Note: saving a seed from one version of QuickCheck and replaying it in another is not supported. If you want to store a test case permanently you should save the test case itself.

- maxSuccess :: Int

  Maximum number of successful tests before succeeding. Testing stops at the first failure. If all tests are passing and you want to run more tests, increase this number.

- maxDiscardRatio :: Int

  Maximum number of discarded tests per successful test before giving up

- maxSize :: Int

  Size to use for the biggest test cases

- chatty :: Bool

  Whether to print anything

- maxShrinks :: Int

  Maximum number of shrinks to do before giving up. Setting this to zero turns shrinking off.

#### Instances

Instances details

Read Args # |
Instance details Defined in Test.QuickCheck.Test Methods readsPrec :: Int -> ReadS Args # readList :: ReadS [Args] # readPrec :: ReadPrec Args # readListPrec :: ReadPrec [Args] #
Show Args # |
Instance details Defined in Test.QuickCheck.Test Methods showsPrec :: Int -> Args -> ShowS # show :: Args -> String # showList :: [Args] -> ShowS #

data Result #

Result represents the test result

Constructors

Success | A successful test run

Fields

- numTests :: Int

  Number of tests performed

- numDiscarded :: Int

  Number of tests skipped

- labels :: !(Map [String] Int)

  The number of test cases having each combination of labels (see `label`)

- classes :: !(Map String Int)

  The number of test cases having each class (see `classify`)

- tables :: !(Map String (Map String Int))

  Data collected by `tabulate`

- output :: String

  Printed output

GaveUp | Given up

Fields

- numTests :: Int

  Number of tests performed

- numDiscarded :: Int

  Number of tests skipped

- labels :: !(Map [String] Int)

  The number of test cases having each combination of labels (see `label`)

- classes :: !(Map String Int)

  The number of test cases having each class (see `classify`)

- tables :: !(Map String (Map String Int))

  Data collected by `tabulate`

- output :: String

  Printed output

Failure | A failed test run

Fields

- numTests :: Int

  Number of tests performed

- numDiscarded :: Int

  Number of tests skipped

- numShrinks :: Int

  Number of successful shrinking steps performed

- numShrinkTries :: Int

  Number of unsuccessful shrinking steps performed

- numShrinkFinal :: Int

  Number of unsuccessful shrinking steps performed since last successful shrink

- usedSeed :: QCGen

  What seed was used

- usedSize :: Int

  What was the test size

- reason :: String

  Why did the property fail

- theException :: Maybe AnException

  The exception the property threw, if any

- output :: String

  Printed output

- failingTestCase :: [String]

  The test case which provoked the failure

- failingLabels :: [String]

  The test case's labels (see `label`)

- failingClasses :: Set String

  The test case's classes (see `classify`)

- witnesses :: [Witness]

  The existentially quantified witnesses provided by `witness`

NoExpectedFailure | A property that should have failed did not

Fields

- numTests :: Int

  Number of tests performed

- numDiscarded :: Int

  Number of tests skipped

- labels :: !(Map [String] Int)

  The number of test cases having each combination of labels (see `label`)

- classes :: !(Map String Int)

  The number of test cases having each class (see `classify`)

- tables :: !(Map String (Map String Int))

  Data collected by `tabulate`

- output :: String

  Printed output

#### Instances

Instances details

Show Result # |
Instance details Defined in Test.QuickCheck.Test Methods showsPrec :: Int -> Result -> ShowS # show :: Result -> String # showList :: [Result] -> ShowS #

stdArgs :: Args #

The default test arguments

quickCheckWith :: Testable prop => Args -> prop -> IO () #

Tests a property, using test arguments, and prints the results to `stdout`.

quickCheckWithResult :: Testable prop => Args -> prop -> IO Result #

Tests a property, using test arguments, produces a test result, and prints the results to `stdout`.

quickCheckResult :: Testable prop => prop -> IO Result #

Tests a property, produces a test result, and prints the results to `stdout`.

recheck :: Testable prop => Result -> prop -> IO () #

Re-run a property with the seed and size that failed in a run of `quickCheckResult`.

isSuccess :: Result -> Bool #

Check if the test run result was a success

## Running tests verbosely

verboseCheck :: Testable prop => prop -> IO () #

Tests a property and prints the results and all test cases generated to `stdout`. This is just a convenience function that means the same as ``quickCheck` . `verbose``.

Note: for technical reasons, the test case is printed out after the property is tested. To debug a property that goes into an infinite loop, use `within` to add a timeout instead.

verboseCheckWith :: Testable prop => Args -> prop -> IO () #

Tests a property, using test arguments, and prints the results and all test cases generated to `stdout`. This is just a convenience function that combines `quickCheckWith` and `verbose`.

Note: for technical reasons, the test case is printed out after the property is tested. To debug a property that goes into an infinite loop, use `within` to add a timeout instead.

verboseCheckWithResult :: Testable prop => Args -> prop -> IO Result #

Tests a property, using test arguments, produces a test result, and prints the results and all test cases generated to `stdout`. This is just a convenience function that combines `quickCheckWithResult` and `verbose`.

Note: for technical reasons, the test case is printed out after the property is tested. To debug a property that goes into an infinite loop, use `within` to add a timeout instead.

verboseCheckResult :: Testable prop => prop -> IO Result #

Tests a property, produces a test result, and prints the results and all test cases generated to `stdout`. This is just a convenience function that combines `quickCheckResult` and `verbose`.

Note: for technical reasons, the test case is printed out after the property is tested. To debug a property that goes into an infinite loop, use `within` to add a timeout instead.

## Testing all properties in a module

These functions test all properties in the current module, using Template Haskell. You need to have a `{-# LANGUAGE TemplateHaskell #-}` pragma in your module for any of these to work.

quickCheckAll :: Q Exp #

Test all properties in the current module. The name of the property must begin with `prop_`. Polymorphic properties will be defaulted to `Integer`. Returns `True` if all tests succeeded, `False` otherwise.

To use `quickCheckAll`, add a definition to your module along the lines of

    return []
    runTests = $quickCheckAll

and then execute `runTests`.

Note: the bizarre `return []` in the example above is needed on GHC 7.8 and later; without it, `quickCheckAll` will not be able to find any of the properties. For the curious, the `return []` is a Template Haskell splice that makes GHC insert the empty list of declarations at that point in the program; GHC typechecks everything before the `return []` before it starts on the rest of the module, which means that the later call to `quickCheckAll` can see everything that was defined before the `return []`. Yikes!

verboseCheckAll :: Q Exp #

Test all properties in the current module. This is just a convenience function that combines `quickCheckAll` and `verbose`.

`verboseCheckAll` has the same issue with scoping as `quickCheckAll`: see the note there about `return []`.

forAllProperties :: Q Exp #

Test all properties in the current module, using a custom `quickCheck` function. The same caveats as with `quickCheckAll` apply.

`$`forAllProperties`` has type `(`Property` -> `IO` `Result`) -> `IO` `Bool``. An example invocation is `$`forAllProperties` `quickCheckResult``, which does the same thing as `$`quickCheckAll``.

`forAllProperties` has the same issue with scoping as `quickCheckAll`: see the note there about `return []`.

allProperties :: Q Exp #

List all properties in the current module.

`$`allProperties`` has type `[(`String`, `Property`)]`.

`allProperties` has the same issue with scoping as `quickCheckAll`: see the note there about `return []`.

## Testing polymorphic properties

polyQuickCheck :: Name -> ExpQ #

Test a polymorphic property, defaulting all type variables to `Integer`.

Invoke as `$(`polyQuickCheck` 'prop)`, where `prop` is a property. Note that just evaluating ``quickCheck` prop` in GHCi will seem to work, but will silently default all type variables to `()`!

`$(`polyQuickCheck` 'prop)` means the same as ``quickCheck` $(`monomorphic` 'prop)`. If you want to supply custom arguments to `polyQuickCheck`, you will have to combine `quickCheckWith` and `monomorphic` yourself.

If you want to use `polyQuickCheck` in the same file where you defined the property, the same scoping problems pop up as in `quickCheckAll`: see the note there about `return []`.

polyVerboseCheck :: Name -> ExpQ #

Test a polymorphic property, defaulting all type variables to `Integer`. This is just a convenience function that combines `verboseCheck` and `monomorphic`.

If you want to use `polyVerboseCheck` in the same file where you defined the property, the same scoping problems pop up as in `quickCheckAll`: see the note there about `return []`.

monomorphic :: Name -> ExpQ #

Monomorphise an arbitrary property by defaulting all type variables to `Integer`.

For example, if `f` has type ``Ord` a => [a] -> [a]` then `$(`monomorphic` 'f)` has type `[`Integer`] -> [`Integer`]`.

If you want to use `monomorphic` in the same file where you defined the property, the same scoping problems pop up as in `quickCheckAll`: see the note there about `return []`.

# The `Arbitrary` typeclass: generation of random values

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 ASCIIString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen ASCIIString # shrink :: ASCIIString -> [ASCIIString] #
Arbitrary PrintableString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen PrintableString # shrink :: PrintableString -> [PrintableString] #
Arbitrary UnicodeString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen UnicodeString # shrink :: UnicodeString -> [UnicodeString] #
Arbitrary A # |
Instance details Defined in Test.QuickCheck.Poly Methods arbitrary :: Gen A # shrink :: A -> [A] #
Arbitrary B # |
Instance details Defined in Test.QuickCheck.Poly Methods arbitrary :: Gen B # shrink :: B -> [B] #
Arbitrary C # |
Instance details Defined in Test.QuickCheck.Poly Methods arbitrary :: Gen C # shrink :: C -> [C] #
Arbitrary OrdA # |
Instance details Defined in Test.QuickCheck.Poly Methods arbitrary :: Gen OrdA # shrink :: OrdA -> [OrdA] #
Arbitrary OrdB # |
Instance details Defined in Test.QuickCheck.Poly Methods arbitrary :: Gen OrdB # shrink :: OrdB -> [OrdB] #
Arbitrary OrdC # |
Instance details Defined in Test.QuickCheck.Poly Methods arbitrary :: Gen OrdC # shrink :: OrdC -> [OrdC] #
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 Version # | Generates `Version` with non-empty non-negative `versionBranch`, and empty `versionTags`
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen Version # shrink :: Version -> [Version] #
Arbitrary CChar # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CChar # shrink :: CChar -> [CChar] #
Arbitrary CClock # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CClock # shrink :: CClock -> [CClock] #
Arbitrary CDouble # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CDouble # shrink :: CDouble -> [CDouble] #
Arbitrary CFloat # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CFloat # shrink :: CFloat -> [CFloat] #
Arbitrary CInt # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CInt # shrink :: CInt -> [CInt] #
Arbitrary CIntMax # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CIntMax # shrink :: CIntMax -> [CIntMax] #
Arbitrary CIntPtr # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CIntPtr # shrink :: CIntPtr -> [CIntPtr] #
Arbitrary CLLong # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CLLong # shrink :: CLLong -> [CLLong] #
Arbitrary CLong # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CLong # shrink :: CLong -> [CLong] #
Arbitrary CPtrdiff # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CPtrdiff # shrink :: CPtrdiff -> [CPtrdiff] #
Arbitrary CSChar # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CSChar # shrink :: CSChar -> [CSChar] #
Arbitrary CSUSeconds # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CSUSeconds # shrink :: CSUSeconds -> [CSUSeconds] #
Arbitrary CShort # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CShort # shrink :: CShort -> [CShort] #
Arbitrary CSigAtomic # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CSigAtomic # shrink :: CSigAtomic -> [CSigAtomic] #
Arbitrary CSize # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CSize # shrink :: CSize -> [CSize] #
Arbitrary CTime # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CTime # shrink :: CTime -> [CTime] #
Arbitrary CUChar # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CUChar # shrink :: CUChar -> [CUChar] #
Arbitrary CUInt # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CUInt # shrink :: CUInt -> [CUInt] #
Arbitrary CUIntMax # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CUIntMax # shrink :: CUIntMax -> [CUIntMax] #
Arbitrary CUIntPtr # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CUIntPtr # shrink :: CUIntPtr -> [CUIntPtr] #
Arbitrary CULLong # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CULLong # shrink :: CULLong -> [CULLong] #
Arbitrary CULong # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CULong # shrink :: CULong -> [CULong] #
Arbitrary CUSeconds # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CUSeconds # shrink :: CUSeconds -> [CUSeconds] #
Arbitrary CUShort # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CUShort # shrink :: CUShort -> [CUShort] #
Arbitrary CWchar # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen CWchar # shrink :: CWchar -> [CWchar] #
Arbitrary ExitCode # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen ExitCode # shrink :: ExitCode -> [ExitCode] #
Arbitrary Newline # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen Newline # shrink :: Newline -> [Newline] #
Arbitrary NewlineMode # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen NewlineMode # shrink :: NewlineMode -> [NewlineMode] #
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 Int8 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen Int8 # shrink :: Int8 -> [Int8] #
Arbitrary Word16 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen Word16 # shrink :: Word16 -> [Word16] #
Arbitrary Word32 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen Word32 # shrink :: Word32 -> [Word32] #
Arbitrary Word64 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen Word64 # shrink :: Word64 -> [Word64] #
Arbitrary Word8 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen Word8 # shrink :: Word8 -> [Word8] #
Arbitrary IntSet # | WARNING: The same warning as for `Arbitrary (Set a)` applies here.
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen IntSet # shrink :: IntSet -> [IntSet] #
Arbitrary Ordering # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen Ordering # shrink :: Ordering -> [Ordering] #
Arbitrary Integer # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen Integer # shrink :: Integer -> [Integer] #
Arbitrary () # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen () # shrink :: () -> [()] #
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 Methods arbitrary :: Gen Double # shrink :: Double -> [Double] #
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 Word # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen Word # shrink :: Word -> [Word] #
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] #
Arbitrary a => Arbitrary (InfiniteList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (InfiniteList a) # shrink :: InfiniteList a -> [InfiniteList a] #
(Integral a, Bounded a) => Arbitrary (Large a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (Large a) # shrink :: Large a -> [Large 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] #
Arbitrary a => Arbitrary (NonEmptyList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (NonEmptyList a) # shrink :: NonEmptyList a -> [NonEmptyList a] #
(Num a, Ord a, Arbitrary a) => Arbitrary (NonNegative a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (NonNegative a) # shrink :: NonNegative a -> [NonNegative a] #
(Num a, Ord a, Arbitrary a) => Arbitrary (NonPositive a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (NonPositive a) # shrink :: NonPositive a -> [NonPositive 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] #
(Ord a, Arbitrary a) => Arbitrary (OrderedList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (OrderedList a) # shrink :: OrderedList a -> [OrderedList a] #
(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] #
Arbitrary a => Arbitrary (Shrink2 a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (Shrink2 a) # shrink :: Shrink2 a -> [Shrink2 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 (Smart a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (Smart a) # shrink :: Smart a -> [Smart a] #
(Arbitrary a, Ord a) => Arbitrary (SortedList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (SortedList a) # shrink :: SortedList a -> [SortedList 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 (Complex a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen (Complex a) # shrink :: Complex a -> [Complex 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 (Product a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen (Product a) # shrink :: Product a -> [Product a] #
Arbitrary a => Arbitrary (Sum a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen (Sum a) # shrink :: Sum a -> [Sum 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 (IntMap a) # | WARNING: The same warning as for `Arbitrary (Set a)` applies here.
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen (IntMap a) # shrink :: IntMap a -> [IntMap a] #
Arbitrary a => Arbitrary (Seq a) # | WARNING: The same warning as for `Arbitrary (Set a)` applies here.
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen (Seq a) # shrink :: Seq a -> [Seq a] #
(Ord a, Arbitrary a) => Arbitrary (Set a) # | WARNING: Users working on the internals of the `Set` type via e.g. `Data.Set.Internal` should be aware that this instance aims to give a good representation of `Set a` as mathematical sets but *does not* aim to provide a varied distribution over the underlying representation.
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen (Set a) # shrink :: Set a -> [Set 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 (Maybe a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen (Maybe a) # shrink :: Maybe a -> [Maybe a] #
Arbitrary a => Arbitrary [a] # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen [a] # shrink :: [a] -> [[a]] #
(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] #
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] #
(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] #
HasResolution a => Arbitrary (Fixed a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen (Fixed a) # shrink :: Fixed a -> [Fixed a] #
(Ord k, Arbitrary k, Arbitrary v) => Arbitrary (Map k v) # | WARNING: The same warning as for `Arbitrary (Set a)` applies here.
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 (a, b) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen (a, b) # shrink :: (a, b) -> [(a, b)] #
(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 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 (a, b, c) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods arbitrary :: Gen (a, b, c) # shrink :: (a, b, c) -> [(a, b, c)] #
(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 (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 (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 (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)] #
(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)] #

## 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.

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`.

shrinkBoundedEnum :: (Bounded a, Enum a, Eq a) => a -> [a] #

Shrink an element of a bounded enumeration.

### Example

Expand

    data MyEnum = E0 | E1 | E2 | E3 | E4 | E5 | E6 | E7 | E8 | E9
       deriving (Bounded, Enum, Eq, Ord, Show)

    >>> shrinkBoundedEnum E9
    [E0,E5,E7,E8]

    >>> shrinkBoundedEnum E5
    [E0,E3,E4]

    >>> shrinkBoundedEnum E0
    []

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

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

## Lifting of `Arbitrary` to unary and binary type constructors

class Arbitrary1 (f :: Type -> Type) 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

Instances details

Arbitrary1 ZipList # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a -> Gen (ZipList a) # liftShrink :: (a -> [a]) -> ZipList a -> [ZipList a] #
Arbitrary1 Identity # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a -> Gen (Identity a) # liftShrink :: (a -> [a]) -> Identity a -> [Identity a] #
Arbitrary1 IntMap # | WARNING: The same warning as for `Arbitrary (Set a)` applies here.
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a -> Gen (IntMap a) # liftShrink :: (a -> [a]) -> IntMap a -> [IntMap a] #
Arbitrary1 Seq # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a -> Gen (Seq a) # liftShrink :: (a -> [a]) -> Seq a -> [Seq a] #
Arbitrary1 Tree # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a -> Gen (Tree a) # liftShrink :: (a -> [a]) -> Tree a -> [Tree a] #
Arbitrary1 Maybe # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a -> Gen (Maybe a) # liftShrink :: (a -> [a]) -> Maybe a -> [Maybe a] #
Arbitrary1 [] # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a -> Gen [a] # liftShrink :: (a -> [a]) -> [a] -> [[a]] #
Arbitrary a => Arbitrary1 (Either a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a0 -> Gen (Either a a0) # liftShrink :: (a0 -> [a0]) -> Either a a0 -> [Either a a0] #
(Ord k, Arbitrary k) => Arbitrary1 (Map k) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a -> Gen (Map k a) # liftShrink :: (a -> [a]) -> Map k a -> [Map k a] #
Arbitrary a => Arbitrary1 ((,) a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a0 -> Gen (a, a0) # liftShrink :: (a0 -> [a0]) -> (a, a0) -> [(a, a0)] #
Arbitrary a => Arbitrary1 (Const a :: Type -> Type) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a0 -> Gen (Const a a0) # liftShrink :: (a0 -> [a0]) -> Const a a0 -> [Const a a0] #
Arbitrary a => Arbitrary1 (Constant a :: Type -> Type) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a0 -> Gen (Constant a a0) # liftShrink :: (a0 -> [a0]) -> Constant a a0 -> [Constant a a0] #
(Arbitrary1 f, Arbitrary1 g) => Arbitrary1 (Product f g) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a -> Gen (Product f g a) # liftShrink :: (a -> [a]) -> Product f g a -> [Product f g a] #
CoArbitrary a => Arbitrary1 ((->) a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary :: Gen a0 -> Gen (a -> a0) # liftShrink :: (a0 -> [a0]) -> (a -> a0) -> [a -> a0] #
(Arbitrary1 f, Arbitrary1 g) => Arbitrary1 (Compose f g) # |
Instance details Defined in Test.QuickCheck.Arbitrary 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 :: Type -> Type -> Type) 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

Instances details

Arbitrary2 Either # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary2 :: Gen a -> Gen b -> Gen (Either a b) # liftShrink2 :: (a -> [a]) -> (b -> [b]) -> Either a b -> [Either a b] #
Arbitrary2 (,) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary2 :: Gen a -> Gen b -> Gen (a, b) # liftShrink2 :: (a -> [a]) -> (b -> [b]) -> (a, b) -> [(a, b)] #
Arbitrary2 (Const :: Type -> Type -> Type) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods liftArbitrary2 :: Gen a -> Gen b -> Gen (Const a b) # liftShrink2 :: (a -> [a]) -> (b -> [b]) -> Const a b -> [Const a b] #
Arbitrary2 (Constant :: Type -> Type -> Type) # |
Instance details Defined in Test.QuickCheck.Arbitrary 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] #

# The `Gen` monad: combinators for building random generators

data Gen a #

A generator for values of type `a`.

The third-party packages QuickCheck-GenT and quickcheck-transformer provide monad transformer versions of `Gen`.

#### Instances

Instances details

MonadFix Gen # |
Instance details Defined in Test.QuickCheck.Gen Methods mfix :: (a -> Gen a) -> Gen a #
Applicative Gen # |
Instance details Defined in Test.QuickCheck.Gen Methods pure :: a -> Gen a # (<*>) :: Gen (a -> b) -> Gen a -> Gen b # liftA2 :: (a -> b -> c) -> Gen a -> Gen b -> Gen c # (*>) :: Gen a -> Gen b -> Gen b # (<*) :: Gen a -> Gen b -> Gen a #
Functor Gen # |
Instance details Defined in Test.QuickCheck.Gen Methods fmap :: (a -> b) -> Gen a -> Gen b # (<$) :: a -> Gen b -> Gen a #
Monad Gen # |
Instance details Defined in Test.QuickCheck.Gen Methods (>>=) :: Gen a -> (a -> Gen b) -> Gen b # (>>) :: Gen a -> Gen b -> Gen b # return :: a -> Gen a #
Testable prop => Testable (Gen prop) # |
Instance details Defined in Test.QuickCheck.Property Methods property :: Gen prop -> Property # propertyForAllShrinkShow :: Gen a -> (a -> [a]) -> (a -> [String]) -> (a -> Gen prop) -> Property #

## Generator combinators

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

Generates a random element in the given inclusive range. For integral and enumerated types, the specialised variants of `choose` below run much quicker.

chooseInt :: (Int, Int) -> Gen Int #

A fast implementation of `choose` for `Int`.

chooseInteger :: (Integer, Integer) -> Gen Integer #

A fast implementation of `choose` for `Integer`.

chooseBoundedIntegral :: (Bounded a, Integral a) => (a, a) -> Gen a #

A fast implementation of `choose` for bounded integral types.

chooseEnum :: Enum a => (a, a) -> Gen a #

A fast implementation of `choose` for enumerated types.

chooseAny :: Random a => Gen a #

Generates a random element over the natural range of `a`.

oneof :: HasCallStack => [Gen a] -> Gen a #

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

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

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

elements :: HasCallStack => [a] -> Gen a #

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

growingElements :: HasCallStack => [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.

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

Used to construct generators that depend on the size parameter.

For example, `listOf`, which uses the size parameter as an upper bound on length of lists it generates, can be defined like this:

    listOf :: Gen a -> Gen [a]
    listOf gen = sized $ \n ->
      do k <- choose (0,n)
         vectorOf k gen

You can also do this using `getSize`.

getSize :: Gen Int #

Returns the size parameter. Used to construct generators that depend on the size parameter.

For example, `listOf`, which uses the size parameter as an upper bound on length of lists it generates, can be defined like this:

    listOf :: Gen a -> Gen [a]
    listOf gen = do
      n <- getSize
      k <- choose (0,n)
      vectorOf k gen

You can also do this using `sized`.

resize :: HasCallStack => Int -> Gen a -> Gen a #

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 #

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

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

Generates a value that satisfies a predicate.

suchThatMap :: Gen a -> (a -> Maybe b) -> Gen b #

Generates a value for which the given function returns a `Just`, and then applies the function.

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

Tries to generate a value that satisfies a predicate. If it fails to do so after enough attempts, returns `Nothing`.

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.

## Generators for lists

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.

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

Generates a list of a given length.

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

Generates an infinite list.

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

Generates an infinite list.

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

Generates a random permutation of the given list.

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

Generates a random subsequence of the given list.

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

Generates an ordered list.

## Generators for particular types

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.

arbitrarySizedFractional :: Fractional a => Gen a #

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

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.

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.

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.

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.

## Running generators

generate :: Gen a -> IO a #

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

## Debugging generators

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

Generates some example values and prints them to `stdout`.

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

Generates some example values.

# The `Function` typeclass: generation of random shrinkable, showable functions

Example of use:

    >>> :{
    >>> let prop :: Fun String Integer -> Bool
    >>> prop (Fun _ f) = f "monkey" == f "banana" || f "banana" == f "elephant"
    >>> :}
    >>> quickCheck prop
    *** Failed! Falsified (after 3 tests and 134 shrinks):
    {"elephant"->1, "monkey"->1, _->0}

To generate random values of type ``Fun` a b`, you must have an instance ``Function` a`. If your type has a `Show` instance, you can use `functionShow` to write the instance; otherwise, use `functionMap` to give a bijection between your type and a type that is already an instance of `Function`. See the ``Function` [a]` instance for an example of the latter.

For more information, see the paper "Shrinking and showing functions" by Koen Claessen.

data Fun a b #

Generation of random shrinkable, showable functions.

To generate random values of type ``Fun` a b`, you must have an instance ``Function` a`.

See also `applyFun`, and `Fn` with GHC >= 7.8.

Constructors

Fun (a :-> b, b, Shrunk) (a -> b) |

#### Instances

Instances details

Functor (Fun a) # |
Instance details Defined in Test.QuickCheck.Function Methods fmap :: (a0 -> b) -> Fun a a0 -> Fun a b # (<$) :: a0 -> Fun a b -> Fun a a0 #
(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] #
(Show a, Show b) => Show (Fun a b) # |
Instance details Defined in Test.QuickCheck.Function Methods showsPrec :: Int -> Fun a b -> ShowS # show :: Fun a b -> String # showList :: [Fun a b] -> ShowS #

applyFun :: Fun a b -> a -> b #

Extracts the value of a function.

`Fn` is the pattern equivalent of this function.

    prop :: Fun String Integer -> Bool
    prop f = applyFun f "banana" == applyFun f "monkey"
          || applyFun f "banana" == applyFun f "elephant"

applyFun2 :: Fun (a, b) c -> a -> b -> c #

Extracts the value of a binary function.

`Fn2` is the pattern equivalent of this function.

    prop_zipWith :: Fun (Int, Bool) Char -> [Int] -> [Bool] -> Bool
    prop_zipWith f xs ys = zipWith (applyFun2 f) xs ys == [ applyFun2 f x y | (x, y) <- zip xs ys]

applyFun3 :: Fun (a, b, c) d -> a -> b -> c -> d #

Extracts the value of a ternary function. `Fn3` is the pattern equivalent of this function.

pattern Fn :: (a -> b) -> Fun a b #

A modifier for testing functions.

    prop :: Fun String Integer -> Bool
    prop (Fn f) = f "banana" == f "monkey"
               || f "banana" == f "elephant"

pattern Fn2 :: (a -> b -> c) -> Fun (a, b) c #

A modifier for testing binary functions.

    prop_zipWith :: Fun (Int, Bool) Char -> [Int] -> [Bool] -> Bool
    prop_zipWith (Fn2 f) xs ys = zipWith f xs ys == [ f x y | (x, y) <- zip xs ys]

pattern Fn3 :: (a -> b -> c -> d) -> Fun (a, b, c) d #

A modifier for testing ternary functions.

class Function a where #

The class `Function a` is used for random generation of showable functions of type `a -> b`.

There is a default implementation for `function`, which you can use if your type has structural equality. Otherwise, you can normally use `functionMap` or `functionShow`.

Minimal complete definition

Nothing

Methods

function :: (a -> b) -> a :-> b #

default function :: (Generic a, GFunction (Rep a)) => (a -> b) -> a :-> b #

#### Instances

Instances details

Function A # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (A -> b) -> A :-> b #
Function B # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (B -> b) -> B :-> b #
Function C # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (C -> b) -> C :-> b #
Function OrdA # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (OrdA -> b) -> OrdA :-> b #
Function OrdB # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (OrdB -> b) -> OrdB :-> b #
Function OrdC # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (OrdC -> b) -> OrdC :-> b #
Function All # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (All -> b) -> All :-> b #
Function Any # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Any -> b) -> Any :-> b #
Function Newline # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Newline -> b) -> Newline :-> b #
Function NewlineMode # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (NewlineMode -> b) -> NewlineMode :-> b #
Function Int16 # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Int16 -> b) -> Int16 :-> b #
Function Int32 # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Int32 -> b) -> Int32 :-> b #
Function Int64 # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Int64 -> b) -> Int64 :-> b #
Function Int8 # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Int8 -> b) -> Int8 :-> b #
Function Word16 # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Word16 -> b) -> Word16 :-> b #
Function Word32 # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Word32 -> b) -> Word32 :-> b #
Function Word64 # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Word64 -> b) -> Word64 :-> b #
Function Word8 # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Word8 -> b) -> Word8 :-> b #
Function IntSet # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (IntSet -> b) -> IntSet :-> b #
Function Ordering # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Ordering -> b) -> Ordering :-> b #
Function Integer # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Integer -> b) -> Integer :-> b #
Function () # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (() -> b) -> () :-> b #
Function Bool # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Bool -> b) -> Bool :-> b #
Function Char # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Char -> b) -> Char :-> b #
Function Double # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Double -> b) -> Double :-> b #
Function Float # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Float -> b) -> Float :-> b #
Function Int # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Int -> b) -> Int :-> b #
Function Word # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Word -> b) -> Word :-> b #
(RealFloat a, Function a) => Function (Complex a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Complex a -> b) -> Complex a :-> b #
Function a => Function (Identity a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Identity a -> b) -> Identity a :-> b #
Function a => Function (First a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (First a -> b) -> First a :-> b #
Function a => Function (Last a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Last a -> b) -> Last a :-> b #
Function a => Function (Dual a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Dual a -> b) -> Dual a :-> b #
Function a => Function (Product a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Product a -> b) -> Product a :-> b #
Function a => Function (Sum a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Sum a -> b) -> Sum a :-> b #
(Integral a, Function a) => Function (Ratio a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Ratio a -> b) -> Ratio a :-> b #
Function a => Function (IntMap a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (IntMap a -> b) -> IntMap a :-> b #
Function a => Function (Seq a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Seq a -> b) -> Seq a :-> b #
(Ord a, Function a) => Function (Set a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Set a -> b) -> Set a :-> b #
Function a => Function (Tree a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Tree a -> b) -> Tree a :-> b #
Function a => Function (Maybe a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Maybe a -> b) -> Maybe a :-> b #
Function a => Function [a] # |
Instance details Defined in Test.QuickCheck.Function Methods function :: ([a] -> b) -> [a] :-> b #
(Function a, Function b) => Function (Either a b) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Either a b -> b0) -> Either a b :-> b0 #
HasResolution a => Function (Fixed a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Fixed a -> b) -> Fixed a :-> b #
(Ord a, Function a, Function b) => Function (Map a b) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Map a b -> b0) -> Map a b :-> b0 #
(Function a, Function b) => Function (a, b) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: ((a, b) -> b0) -> (a, b) :-> b0 #
Function a => Function (Const a b) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Const a b -> b0) -> Const a b :-> b0 #
Function (f a) => Function (Alt f a) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: (Alt f a -> b) -> Alt f a :-> b #
(Function a, Function b, Function c) => Function (a, b, c) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: ((a, b, c) -> b0) -> (a, b, c) :-> b0 #
(Function a, Function b, Function c, Function d) => Function (a, b, c, d) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: ((a, b, c, d) -> b0) -> (a, b, c, d) :-> b0 #
(Function a, Function b, Function c, Function d, Function e) => Function (a, b, c, d, e) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: ((a, b, c, d, e) -> b0) -> (a, b, c, d, e) :-> b0 #
(Function a, Function b, Function c, Function d, Function e, Function f) => Function (a, b, c, d, e, f) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: ((a, b, c, d, e, f) -> b0) -> (a, b, c, d, e, f) :-> b0 #
(Function a, Function b, Function c, Function d, Function e, Function f, Function g) => Function (a, b, c, d, e, f, g) # |
Instance details Defined in Test.QuickCheck.Function Methods function :: ((a, b, c, d, e, f, g) -> b0) -> (a, b, c, d, e, f, g) :-> b0 #

functionMap :: Function b => (a -> b) -> (b -> a) -> (a -> c) -> a :-> c #

The basic building block for `Function` instances. Provides a `Function` instance by mapping to and from a type that already has a `Function` instance.

functionShow :: (Show a, Read a) => (a -> c) -> a :-> c #

Provides a `Function` instance for types with `Show` and `Read`.

functionIntegral :: Integral a => (a -> b) -> a :-> b #

Provides a `Function` instance for types with `Integral`.

functionRealFrac :: RealFrac a => (a -> b) -> a :-> b #

Provides a `Function` instance for types with `RealFrac`.

functionBoundedEnum :: (Eq a, Bounded a, Enum a) => (a -> b) -> a :-> b #

Provides a `Function` instance for types with `Bounded` and `Enum`. Use only for small types (i.e. not integers): creates the list `[`minBound`..`maxBound`]`!

functionVoid :: (forall b. void -> b) -> void :-> c #

Provides a `Function` instance for types isomorphic to `Void`.

An actual ``Function` `Void`` instance is defined in `quickcheck-instances`.

# The `CoArbitrary` typeclass: generation of functions the old-fashioned way

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)`.

Minimal complete definition

Nothing

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)

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

#### Instances

Instances details

CoArbitrary A # |
Instance details Defined in Test.QuickCheck.Poly Methods coarbitrary :: A -> Gen b -> Gen b #
CoArbitrary B # |
Instance details Defined in Test.QuickCheck.Poly Methods coarbitrary :: B -> Gen b -> Gen b #
CoArbitrary C # |
Instance details Defined in Test.QuickCheck.Poly Methods coarbitrary :: C -> Gen b -> Gen b #
CoArbitrary OrdA # |
Instance details Defined in Test.QuickCheck.Poly Methods coarbitrary :: OrdA -> Gen b -> Gen b #
CoArbitrary OrdB # |
Instance details Defined in Test.QuickCheck.Poly Methods coarbitrary :: OrdB -> Gen b -> Gen b #
CoArbitrary OrdC # |
Instance details Defined in Test.QuickCheck.Poly Methods coarbitrary :: OrdC -> Gen b -> Gen b #
CoArbitrary All # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: All -> Gen b -> Gen b #
CoArbitrary Any # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Any -> Gen b -> Gen b #
CoArbitrary Version # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Version -> Gen b -> Gen b #
CoArbitrary Newline # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Newline -> Gen b -> Gen b #
CoArbitrary NewlineMode # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: NewlineMode -> Gen b -> Gen b #
CoArbitrary Int16 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Int16 -> Gen b -> Gen b #
CoArbitrary Int32 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Int32 -> Gen b -> Gen b #
CoArbitrary Int64 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Int64 -> Gen b -> Gen b #
CoArbitrary Int8 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Int8 -> Gen b -> Gen b #
CoArbitrary Word16 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Word16 -> Gen b -> Gen b #
CoArbitrary Word32 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Word32 -> Gen b -> Gen b #
CoArbitrary Word64 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Word64 -> Gen b -> Gen b #
CoArbitrary Word8 # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Word8 -> Gen b -> Gen b #
CoArbitrary IntSet # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: IntSet -> Gen b -> Gen b #
CoArbitrary Ordering # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Ordering -> Gen b -> Gen b #
CoArbitrary Integer # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Integer -> Gen b -> Gen b #
CoArbitrary () # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: () -> Gen b -> Gen b #
CoArbitrary Bool # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Bool -> Gen b -> Gen b #
CoArbitrary Char # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Char -> Gen b -> Gen b #
CoArbitrary Double # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Double -> Gen b -> Gen b #
CoArbitrary Float # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Float -> Gen b -> Gen b #
CoArbitrary Int # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Int -> Gen b -> Gen b #
CoArbitrary Word # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Word -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (ZipList a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: ZipList a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (Complex a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Complex a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (Identity a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Identity a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (First a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: First a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (Last a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Last a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (Dual a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Dual a -> Gen b -> Gen b #
(Arbitrary a, CoArbitrary a) => CoArbitrary (Endo a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Endo a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (Product a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Product a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (Sum a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Sum a -> Gen b -> Gen b #
(Integral a, CoArbitrary a) => CoArbitrary (Ratio a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Ratio a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (IntMap a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: IntMap a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (Seq a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Seq a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (Set a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Set a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (Tree a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Tree a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (Maybe a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Maybe a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary [a] # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: [a] -> Gen b -> Gen b #
(CoArbitrary a, CoArbitrary b) => CoArbitrary (Either a b) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Either a b -> Gen b0 -> Gen b0 #
HasResolution a => CoArbitrary (Fixed a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Fixed a -> Gen b -> Gen b #
(CoArbitrary k, CoArbitrary v) => CoArbitrary (Map k v) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Map k v -> Gen b -> Gen b #
(CoArbitrary a, CoArbitrary b) => CoArbitrary (a, b) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: (a, b) -> Gen b0 -> Gen b0 #
(Arbitrary a, CoArbitrary b) => CoArbitrary (a -> b) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: (a -> b) -> Gen b0 -> Gen b0 #
CoArbitrary a => CoArbitrary (Const a b) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Const a b -> Gen b0 -> Gen b0 #
CoArbitrary (f a) => CoArbitrary (Alt f a) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Alt f a -> Gen b -> Gen b #
CoArbitrary a => CoArbitrary (Constant a b) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: Constant a b -> Gen b0 -> Gen b0 #
(CoArbitrary a, CoArbitrary b, CoArbitrary c) => CoArbitrary (a, b, c) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: (a, b, c) -> Gen b0 -> Gen b0 #
(CoArbitrary a, CoArbitrary b, CoArbitrary c, CoArbitrary d) => CoArbitrary (a, b, c, d) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: (a, b, c, d) -> Gen b0 -> Gen b0 #
(CoArbitrary a, CoArbitrary b, CoArbitrary c, CoArbitrary d, CoArbitrary e) => CoArbitrary (a, b, c, d, e) # |
Instance details Defined in Test.QuickCheck.Arbitrary Methods coarbitrary :: (a, b, c, d, e) -> Gen b0 -> Gen b0 #

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

Generic CoArbitrary implementation.

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

Modifies a generator using an integer seed.

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`.

# Type-level modifiers for changing generator behavior

These types do things such as restricting the kind of test data that can be generated. They can be pattern-matched on in properties as a stylistic alternative to using explicit quantification.

Examples:

    -- Functions cannot be shown (but see Function)
    prop_TakeDropWhile (Blind p) (xs :: [A]) =
      takeWhile p xs ++ dropWhile p xs == xs

    prop_TakeDrop (NonNegative n) (xs :: [A]) =
      take n xs ++ drop n xs == xs

    -- cycle does not work for empty lists
    prop_Cycle (NonNegative n) (NonEmpty (xs :: [A])) =
      take n (cycle xs) == take n (xs ++ cycle xs)

    -- Instead of forAll orderedList
    prop_Sort (Ordered (xs :: [OrdA])) =
      sort xs == xs

newtype Blind a #

`Blind x`: as x, but x does not have to be in the `Show` class.

Constructors

Blind |

Fields

- getBlind :: a

#### Instances

Instances details

Functor Blind # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> Blind a -> Blind b # (<$) :: a -> Blind b -> Blind a #
Arbitrary a => Arbitrary (Blind a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (Blind a) # shrink :: Blind a -> [Blind a] #
Enum a => Enum (Blind a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods succ :: Blind a -> Blind a # pred :: Blind a -> Blind a # toEnum :: Int -> Blind a # fromEnum :: Blind a -> Int # enumFrom :: Blind a -> [Blind a] # enumFromThen :: Blind a -> Blind a -> [Blind a] # enumFromTo :: Blind a -> Blind a -> [Blind a] # enumFromThenTo :: Blind a -> Blind a -> Blind a -> [Blind a] #
Num a => Num (Blind a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (+) :: Blind a -> Blind a -> Blind a # (-) :: Blind a -> Blind a -> Blind a # (*) :: Blind a -> Blind a -> Blind a # negate :: Blind a -> Blind a # abs :: Blind a -> Blind a # signum :: Blind a -> Blind a # fromInteger :: Integer -> Blind a #
Integral a => Integral (Blind a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods quot :: Blind a -> Blind a -> Blind a # rem :: Blind a -> Blind a -> Blind a # div :: Blind a -> Blind a -> Blind a # mod :: Blind a -> Blind a -> Blind a # quotRem :: Blind a -> Blind a -> (Blind a, Blind a) # divMod :: Blind a -> Blind a -> (Blind a, Blind a) # toInteger :: Blind a -> Integer #
Real a => Real (Blind a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods toRational :: Blind a -> Rational #
Show (Blind a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> Blind a -> ShowS # show :: Blind a -> String # showList :: [Blind a] -> ShowS #
Eq a => Eq (Blind a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: Blind a -> Blind a -> Bool # (/=) :: Blind a -> Blind a -> Bool #
Ord a => Ord (Blind a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods compare :: Blind a -> Blind a -> Ordering # (<) :: Blind a -> Blind a -> Bool # (<=) :: Blind a -> Blind a -> Bool # (>) :: Blind a -> Blind a -> Bool # (>=) :: Blind a -> Blind a -> Bool # max :: Blind a -> Blind a -> Blind a # min :: Blind a -> Blind a -> Blind a #

newtype Fixed a #

`Fixed x`: as x, but will not be shrunk.

Constructors

Fixed |

Fields

- getFixed :: a

#### Instances

Instances details

Functor Fixed # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> Fixed a -> Fixed b # (<$) :: a -> Fixed b -> Fixed a #
Arbitrary a => Arbitrary (Fixed a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (Fixed a) # shrink :: Fixed a -> [Fixed a] #
Enum a => Enum (Fixed a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods succ :: Fixed a -> Fixed a # pred :: Fixed a -> Fixed a # toEnum :: Int -> Fixed a # fromEnum :: Fixed a -> Int # enumFrom :: Fixed a -> [Fixed a] # enumFromThen :: Fixed a -> Fixed a -> [Fixed a] # enumFromTo :: Fixed a -> Fixed a -> [Fixed a] # enumFromThenTo :: Fixed a -> Fixed a -> Fixed a -> [Fixed a] #
Num a => Num (Fixed a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (+) :: Fixed a -> Fixed a -> Fixed a # (-) :: Fixed a -> Fixed a -> Fixed a # (*) :: Fixed a -> Fixed a -> Fixed a # negate :: Fixed a -> Fixed a # abs :: Fixed a -> Fixed a # signum :: Fixed a -> Fixed a # fromInteger :: Integer -> Fixed a #
Read a => Read (Fixed a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS (Fixed a) # readList :: ReadS [Fixed a] # readPrec :: ReadPrec (Fixed a) # readListPrec :: ReadPrec [Fixed a] #
Integral a => Integral (Fixed a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods quot :: Fixed a -> Fixed a -> Fixed a # rem :: Fixed a -> Fixed a -> Fixed a # div :: Fixed a -> Fixed a -> Fixed a # mod :: Fixed a -> Fixed a -> Fixed a # quotRem :: Fixed a -> Fixed a -> (Fixed a, Fixed a) # divMod :: Fixed a -> Fixed a -> (Fixed a, Fixed a) # toInteger :: Fixed a -> Integer #
Real a => Real (Fixed a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods toRational :: Fixed a -> Rational #
Show a => Show (Fixed a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> Fixed a -> ShowS # show :: Fixed a -> String # showList :: [Fixed a] -> ShowS #
Eq a => Eq (Fixed a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: Fixed a -> Fixed a -> Bool # (/=) :: Fixed a -> Fixed a -> Bool #
Ord a => Ord (Fixed a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods compare :: Fixed a -> Fixed a -> Ordering # (<) :: Fixed a -> Fixed a -> Bool # (<=) :: Fixed a -> Fixed a -> Bool # (>) :: Fixed a -> Fixed a -> Bool # (>=) :: Fixed a -> Fixed a -> Bool # max :: Fixed a -> Fixed a -> Fixed a # min :: Fixed a -> Fixed a -> Fixed a #

newtype OrderedList a #

`Ordered xs`: guarantees that xs is ordered.

Constructors

Ordered |

Fields

- getOrdered :: [a]

#### Instances

Instances details

Functor OrderedList # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> OrderedList a -> OrderedList b # (<$) :: a -> OrderedList b -> OrderedList a #
(Ord a, Arbitrary a) => Arbitrary (OrderedList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (OrderedList a) # shrink :: OrderedList a -> [OrderedList a] #
Read a => Read (OrderedList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS (OrderedList a) # readList :: ReadS [OrderedList a] # readPrec :: ReadPrec (OrderedList a) # readListPrec :: ReadPrec [OrderedList a] #
Show a => Show (OrderedList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> OrderedList a -> ShowS # show :: OrderedList a -> String # showList :: [OrderedList a] -> ShowS #
Eq a => Eq (OrderedList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: OrderedList a -> OrderedList a -> Bool # (/=) :: OrderedList a -> OrderedList a -> Bool #
Ord a => Ord (OrderedList a) # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

compare :: OrderedList a -> OrderedList a -> Ordering #

(<) :: OrderedList a -> OrderedList a -> Bool #

(<=) :: OrderedList a -> OrderedList a -> Bool #

(>) :: OrderedList a -> OrderedList a -> Bool #

(>=) :: OrderedList a -> OrderedList a -> Bool #

max :: OrderedList a -> OrderedList a -> OrderedList a #

min :: OrderedList a -> OrderedList a -> OrderedList a #

newtype NonEmptyList a #

`NonEmpty xs`: guarantees that xs is non-empty.

Constructors

NonEmpty |

Fields

- getNonEmpty :: [a]

#### Instances

Instances details

Functor NonEmptyList # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> NonEmptyList a -> NonEmptyList b # (<$) :: a -> NonEmptyList b -> NonEmptyList a #
Arbitrary a => Arbitrary (NonEmptyList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (NonEmptyList a) # shrink :: NonEmptyList a -> [NonEmptyList a] #
Read a => Read (NonEmptyList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS (NonEmptyList a) # readList :: ReadS [NonEmptyList a] # readPrec :: ReadPrec (NonEmptyList a) # readListPrec :: ReadPrec [NonEmptyList a] #
Show a => Show (NonEmptyList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> NonEmptyList a -> ShowS # show :: NonEmptyList a -> String # showList :: [NonEmptyList a] -> ShowS #
Eq a => Eq (NonEmptyList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: NonEmptyList a -> NonEmptyList a -> Bool # (/=) :: NonEmptyList a -> NonEmptyList a -> Bool #
Ord a => Ord (NonEmptyList a) # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

compare :: NonEmptyList a -> NonEmptyList a -> Ordering #

(<) :: NonEmptyList a -> NonEmptyList a -> Bool #

(<=) :: NonEmptyList a -> NonEmptyList a -> Bool #

(>) :: NonEmptyList a -> NonEmptyList a -> Bool #

(>=) :: NonEmptyList a -> NonEmptyList a -> Bool #

max :: NonEmptyList a -> NonEmptyList a -> NonEmptyList a #

min :: NonEmptyList a -> NonEmptyList a -> NonEmptyList a #

data InfiniteList a #

`InfiniteList xs _`: guarantees that xs is an infinite list. When a counterexample is found, only prints the prefix of xs that was used by the program.

Here is a contrived example property:

    prop_take_10 :: InfiniteList Char -> Bool
    prop_take_10 (InfiniteList xs _) =
      or [ x == 'a' | x <- take 10 xs ]

In the following counterexample, the list must start with `"bbbbbbbbbb"` but the remaining (infinite) part can contain anything:

    >>> quickCheck prop_take_10
    *** Failed! Falsified (after 1 test and 14 shrinks):
    "bbbbbbbbbb" ++ ...

Constructors

InfiniteList |

Fields

- getInfiniteList :: [a]
- infiniteListInternalData :: InfiniteListInternalData a

#### Instances

Instances details

Arbitrary a => Arbitrary (InfiniteList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (InfiniteList a) # shrink :: InfiniteList a -> [InfiniteList a] #
Show a => Show (InfiniteList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> InfiniteList a -> ShowS # show :: InfiniteList a -> String # showList :: [InfiniteList a] -> ShowS #

newtype SortedList a #

`Sorted xs`: guarantees that xs is sorted.

Constructors

Sorted |

Fields

- getSorted :: [a]

#### Instances

Instances details

Functor SortedList # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> SortedList a -> SortedList b # (<$) :: a -> SortedList b -> SortedList a #
(Arbitrary a, Ord a) => Arbitrary (SortedList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (SortedList a) # shrink :: SortedList a -> [SortedList a] #
Read a => Read (SortedList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS (SortedList a) # readList :: ReadS [SortedList a] # readPrec :: ReadPrec (SortedList a) # readListPrec :: ReadPrec [SortedList a] #
Show a => Show (SortedList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> SortedList a -> ShowS # show :: SortedList a -> String # showList :: [SortedList a] -> ShowS #
Eq a => Eq (SortedList a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: SortedList a -> SortedList a -> Bool # (/=) :: SortedList a -> SortedList a -> Bool #
Ord a => Ord (SortedList a) # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

compare :: SortedList a -> SortedList a -> Ordering #

(<) :: SortedList a -> SortedList a -> Bool #

(<=) :: SortedList a -> SortedList a -> Bool #

(>) :: SortedList a -> SortedList a -> Bool #

(>=) :: SortedList a -> SortedList a -> Bool #

max :: SortedList a -> SortedList a -> SortedList a #

min :: SortedList a -> SortedList a -> SortedList a #

newtype Positive a #

`Positive x`: guarantees that `x > 0`.

Constructors

Positive |

Fields

- getPositive :: a

#### Instances

Instances details

Functor Positive # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> Positive a -> Positive b # (<$) :: a -> Positive b -> Positive a #
(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] #
Enum a => Enum (Positive a) # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

succ :: Positive a -> Positive a #

pred :: Positive a -> Positive a #

toEnum :: Int -> Positive a #

fromEnum :: Positive a -> Int #

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

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

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

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

Read a => Read (Positive a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS (Positive a) # readList :: ReadS [Positive a] # readPrec :: ReadPrec (Positive a) # readListPrec :: ReadPrec [Positive a] #
Show a => Show (Positive a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> Positive a -> ShowS # show :: Positive a -> String # showList :: [Positive a] -> ShowS #
Eq a => Eq (Positive a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: Positive a -> Positive a -> Bool # (/=) :: Positive a -> Positive a -> Bool #
Ord a => Ord (Positive a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods compare :: Positive a -> Positive a -> Ordering # (<) :: Positive a -> Positive a -> Bool # (<=) :: Positive a -> Positive a -> Bool # (>) :: Positive a -> Positive a -> Bool # (>=) :: Positive a -> Positive a -> Bool # max :: Positive a -> Positive a -> Positive a # min :: Positive a -> Positive a -> Positive a #

newtype Negative a #

`Negative x`: guarantees that `x < 0`.

Constructors

Negative |

Fields

- getNegative :: a

#### Instances

Instances details

Functor Negative # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> Negative a -> Negative b # (<$) :: a -> Negative b -> Negative 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] #
Enum a => Enum (Negative a) # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

succ :: Negative a -> Negative a #

pred :: Negative a -> Negative a #

toEnum :: Int -> Negative a #

fromEnum :: Negative a -> Int #

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

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

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

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

Read a => Read (Negative a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS (Negative a) # readList :: ReadS [Negative a] # readPrec :: ReadPrec (Negative a) # readListPrec :: ReadPrec [Negative a] #
Show a => Show (Negative a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> Negative a -> ShowS # show :: Negative a -> String # showList :: [Negative a] -> ShowS #
Eq a => Eq (Negative a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: Negative a -> Negative a -> Bool # (/=) :: Negative a -> Negative a -> Bool #
Ord a => Ord (Negative a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods compare :: Negative a -> Negative a -> Ordering # (<) :: Negative a -> Negative a -> Bool # (<=) :: Negative a -> Negative a -> Bool # (>) :: Negative a -> Negative a -> Bool # (>=) :: Negative a -> Negative a -> Bool # max :: Negative a -> Negative a -> Negative a # min :: Negative a -> Negative a -> Negative a #

newtype NonZero a #

`NonZero x`: guarantees that `x /= 0`.

Constructors

NonZero |

Fields

- getNonZero :: a

#### Instances

Instances details

Functor NonZero # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> NonZero a -> NonZero b # (<$) :: a -> NonZero b -> NonZero 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] #
Enum a => Enum (NonZero a) # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

succ :: NonZero a -> NonZero a #

pred :: NonZero a -> NonZero a #

toEnum :: Int -> NonZero a #

fromEnum :: NonZero a -> Int #

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

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

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

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

Read a => Read (NonZero a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS (NonZero a) # readList :: ReadS [NonZero a] # readPrec :: ReadPrec (NonZero a) # readListPrec :: ReadPrec [NonZero a] #
Show a => Show (NonZero a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> NonZero a -> ShowS # show :: NonZero a -> String # showList :: [NonZero a] -> ShowS #
Eq a => Eq (NonZero a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: NonZero a -> NonZero a -> Bool # (/=) :: NonZero a -> NonZero a -> Bool #
Ord a => Ord (NonZero a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods compare :: NonZero a -> NonZero a -> Ordering # (<) :: NonZero a -> NonZero a -> Bool # (<=) :: NonZero a -> NonZero a -> Bool # (>) :: NonZero a -> NonZero a -> Bool # (>=) :: NonZero a -> NonZero a -> Bool # max :: NonZero a -> NonZero a -> NonZero a # min :: NonZero a -> NonZero a -> NonZero a #

newtype NonNegative a #

`NonNegative x`: guarantees that `x >= 0`.

Constructors

NonNegative |

Fields

- getNonNegative :: a

#### Instances

Instances details

Functor NonNegative # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> NonNegative a -> NonNegative b # (<$) :: a -> NonNegative b -> NonNegative a #
(Num a, Ord a, Arbitrary a) => Arbitrary (NonNegative a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (NonNegative a) # shrink :: NonNegative a -> [NonNegative a] #
Enum a => Enum (NonNegative a) # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

succ :: NonNegative a -> NonNegative a #

pred :: NonNegative a -> NonNegative a #

toEnum :: Int -> NonNegative a #

fromEnum :: NonNegative a -> Int #

enumFrom :: NonNegative a -> [NonNegative a] #

enumFromThen :: NonNegative a -> NonNegative a -> [NonNegative a] #

enumFromTo :: NonNegative a -> NonNegative a -> [NonNegative a] #

enumFromThenTo :: NonNegative a -> NonNegative a -> NonNegative a -> [NonNegative a] #

Read a => Read (NonNegative a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS (NonNegative a) # readList :: ReadS [NonNegative a] # readPrec :: ReadPrec (NonNegative a) # readListPrec :: ReadPrec [NonNegative a] #
Show a => Show (NonNegative a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> NonNegative a -> ShowS # show :: NonNegative a -> String # showList :: [NonNegative a] -> ShowS #
Eq a => Eq (NonNegative a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: NonNegative a -> NonNegative a -> Bool # (/=) :: NonNegative a -> NonNegative a -> Bool #
Ord a => Ord (NonNegative a) # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

compare :: NonNegative a -> NonNegative a -> Ordering #

(<) :: NonNegative a -> NonNegative a -> Bool #

(<=) :: NonNegative a -> NonNegative a -> Bool #

(>) :: NonNegative a -> NonNegative a -> Bool #

(>=) :: NonNegative a -> NonNegative a -> Bool #

max :: NonNegative a -> NonNegative a -> NonNegative a #

min :: NonNegative a -> NonNegative a -> NonNegative a #

newtype NonPositive a #

`NonPositive x`: guarantees that `x <= 0`.

Constructors

NonPositive |

Fields

- getNonPositive :: a

#### Instances

Instances details

Functor NonPositive # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> NonPositive a -> NonPositive b # (<$) :: a -> NonPositive b -> NonPositive a #
(Num a, Ord a, Arbitrary a) => Arbitrary (NonPositive a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (NonPositive a) # shrink :: NonPositive a -> [NonPositive a] #
Enum a => Enum (NonPositive a) # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

succ :: NonPositive a -> NonPositive a #

pred :: NonPositive a -> NonPositive a #

toEnum :: Int -> NonPositive a #

fromEnum :: NonPositive a -> Int #

enumFrom :: NonPositive a -> [NonPositive a] #

enumFromThen :: NonPositive a -> NonPositive a -> [NonPositive a] #

enumFromTo :: NonPositive a -> NonPositive a -> [NonPositive a] #

enumFromThenTo :: NonPositive a -> NonPositive a -> NonPositive a -> [NonPositive a] #

Read a => Read (NonPositive a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS (NonPositive a) # readList :: ReadS [NonPositive a] # readPrec :: ReadPrec (NonPositive a) # readListPrec :: ReadPrec [NonPositive a] #
Show a => Show (NonPositive a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> NonPositive a -> ShowS # show :: NonPositive a -> String # showList :: [NonPositive a] -> ShowS #
Eq a => Eq (NonPositive a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: NonPositive a -> NonPositive a -> Bool # (/=) :: NonPositive a -> NonPositive a -> Bool #
Ord a => Ord (NonPositive a) # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

compare :: NonPositive a -> NonPositive a -> Ordering #

(<) :: NonPositive a -> NonPositive a -> Bool #

(<=) :: NonPositive a -> NonPositive a -> Bool #

(>) :: NonPositive a -> NonPositive a -> Bool #

(>=) :: NonPositive a -> NonPositive a -> Bool #

max :: NonPositive a -> NonPositive a -> NonPositive a #

min :: NonPositive a -> NonPositive a -> NonPositive a #

newtype Large a #

`Large x`: by default, QuickCheck generates `Int`s drawn from a small range. `Large Int` gives you values drawn from the entire range instead.

Constructors

Large |

Fields

- getLarge :: a

#### Instances

Instances details

Functor Large # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> Large a -> Large b # (<$) :: a -> Large b -> Large a #
(Integral a, Bounded a) => Arbitrary (Large a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (Large a) # shrink :: Large a -> [Large a] #
Enum a => Enum (Large a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods succ :: Large a -> Large a # pred :: Large a -> Large a # toEnum :: Int -> Large a # fromEnum :: Large a -> Int # enumFrom :: Large a -> [Large a] # enumFromThen :: Large a -> Large a -> [Large a] # enumFromTo :: Large a -> Large a -> [Large a] # enumFromThenTo :: Large a -> Large a -> Large a -> [Large a] #
Ix a => Ix (Large a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods range :: (Large a, Large a) -> [Large a] # index :: (Large a, Large a) -> Large a -> Int # unsafeIndex :: (Large a, Large a) -> Large a -> Int # inRange :: (Large a, Large a) -> Large a -> Bool # rangeSize :: (Large a, Large a) -> Int # unsafeRangeSize :: (Large a, Large a) -> Int #
Num a => Num (Large a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (+) :: Large a -> Large a -> Large a # (-) :: Large a -> Large a -> Large a # (*) :: Large a -> Large a -> Large a # negate :: Large a -> Large a # abs :: Large a -> Large a # signum :: Large a -> Large a # fromInteger :: Integer -> Large a #
Read a => Read (Large a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS (Large a) # readList :: ReadS [Large a] # readPrec :: ReadPrec (Large a) # readListPrec :: ReadPrec [Large a] #
Integral a => Integral (Large a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods quot :: Large a -> Large a -> Large a # rem :: Large a -> Large a -> Large a # div :: Large a -> Large a -> Large a # mod :: Large a -> Large a -> Large a # quotRem :: Large a -> Large a -> (Large a, Large a) # divMod :: Large a -> Large a -> (Large a, Large a) # toInteger :: Large a -> Integer #
Real a => Real (Large a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods toRational :: Large a -> Rational #
Show a => Show (Large a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> Large a -> ShowS # show :: Large a -> String # showList :: [Large a] -> ShowS #
Eq a => Eq (Large a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: Large a -> Large a -> Bool # (/=) :: Large a -> Large a -> Bool #
Ord a => Ord (Large a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods compare :: Large a -> Large a -> Ordering # (<) :: Large a -> Large a -> Bool # (<=) :: Large a -> Large a -> Bool # (>) :: Large a -> Large a -> Bool # (>=) :: Large a -> Large a -> Bool # max :: Large a -> Large a -> Large a # min :: Large a -> Large a -> Large a #

newtype Small a #

`Small x`: generates values of `x` drawn from a small range. The opposite of `Large`.

Constructors

Small |

Fields

- getSmall :: a

#### Instances

Instances details

Functor Small # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> Small a -> Small b # (<$) :: a -> Small b -> Small a #
Integral a => Arbitrary (Small a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (Small a) # shrink :: Small a -> [Small a] #
Enum a => Enum (Small a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods succ :: Small a -> Small a # pred :: Small a -> Small a # toEnum :: Int -> Small a # fromEnum :: Small a -> Int # enumFrom :: Small a -> [Small a] # enumFromThen :: Small a -> Small a -> [Small a] # enumFromTo :: Small a -> Small a -> [Small a] # enumFromThenTo :: Small a -> Small a -> Small a -> [Small a] #
Ix a => Ix (Small a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods range :: (Small a, Small a) -> [Small a] # index :: (Small a, Small a) -> Small a -> Int # unsafeIndex :: (Small a, Small a) -> Small a -> Int # inRange :: (Small a, Small a) -> Small a -> Bool # rangeSize :: (Small a, Small a) -> Int # unsafeRangeSize :: (Small a, Small a) -> Int #
Num a => Num (Small a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (+) :: Small a -> Small a -> Small a # (-) :: Small a -> Small a -> Small a # (*) :: Small a -> Small a -> Small a # negate :: Small a -> Small a # abs :: Small a -> Small a # signum :: Small a -> Small a # fromInteger :: Integer -> Small a #
Read a => Read (Small a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS (Small a) # readList :: ReadS [Small a] # readPrec :: ReadPrec (Small a) # readListPrec :: ReadPrec [Small a] #
Integral a => Integral (Small a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods quot :: Small a -> Small a -> Small a # rem :: Small a -> Small a -> Small a # div :: Small a -> Small a -> Small a # mod :: Small a -> Small a -> Small a # quotRem :: Small a -> Small a -> (Small a, Small a) # divMod :: Small a -> Small a -> (Small a, Small a) # toInteger :: Small a -> Integer #
Real a => Real (Small a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods toRational :: Small a -> Rational #
Show a => Show (Small a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> Small a -> ShowS # show :: Small a -> String # showList :: [Small a] -> ShowS #
Eq a => Eq (Small a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: Small a -> Small a -> Bool # (/=) :: Small a -> Small a -> Bool #
Ord a => Ord (Small a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods compare :: Small a -> Small a -> Ordering # (<) :: Small a -> Small a -> Bool # (<=) :: Small a -> Small a -> Bool # (>) :: Small a -> Small a -> Bool # (>=) :: Small a -> Small a -> Bool # max :: Small a -> Small a -> Small a # min :: Small a -> Small a -> Small a #

data Smart a #

`Smart _ x`: tries a different order when shrinking.

Constructors

Smart Int a |

#### Instances

Instances details

Functor Smart # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> Smart a -> Smart b # (<$) :: a -> Smart b -> Smart a #
Arbitrary a => Arbitrary (Smart a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (Smart a) # shrink :: Smart a -> [Smart a] #
Show a => Show (Smart a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> Smart a -> ShowS # show :: Smart a -> String # showList :: [Smart a] -> ShowS #

newtype Shrink2 a #

`Shrink2 x`: allows 2 shrinking steps at the same time when shrinking x

Constructors

Shrink2 |

Fields

- getShrink2 :: a

#### Instances

Instances details

Functor Shrink2 # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> Shrink2 a -> Shrink2 b # (<$) :: a -> Shrink2 b -> Shrink2 a #
Arbitrary a => Arbitrary (Shrink2 a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen (Shrink2 a) # shrink :: Shrink2 a -> [Shrink2 a] #
Enum a => Enum (Shrink2 a) # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

succ :: Shrink2 a -> Shrink2 a #

pred :: Shrink2 a -> Shrink2 a #

toEnum :: Int -> Shrink2 a #

fromEnum :: Shrink2 a -> Int #

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

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

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

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

Num a => Num (Shrink2 a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (+) :: Shrink2 a -> Shrink2 a -> Shrink2 a # (-) :: Shrink2 a -> Shrink2 a -> Shrink2 a # (*) :: Shrink2 a -> Shrink2 a -> Shrink2 a # negate :: Shrink2 a -> Shrink2 a # abs :: Shrink2 a -> Shrink2 a # signum :: Shrink2 a -> Shrink2 a # fromInteger :: Integer -> Shrink2 a #
Read a => Read (Shrink2 a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS (Shrink2 a) # readList :: ReadS [Shrink2 a] # readPrec :: ReadPrec (Shrink2 a) # readListPrec :: ReadPrec [Shrink2 a] #
Integral a => Integral (Shrink2 a) # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

quot :: Shrink2 a -> Shrink2 a -> Shrink2 a #

rem :: Shrink2 a -> Shrink2 a -> Shrink2 a #

div :: Shrink2 a -> Shrink2 a -> Shrink2 a #

mod :: Shrink2 a -> Shrink2 a -> Shrink2 a #

quotRem :: Shrink2 a -> Shrink2 a -> (Shrink2 a, Shrink2 a) #

divMod :: Shrink2 a -> Shrink2 a -> (Shrink2 a, Shrink2 a) #

toInteger :: Shrink2 a -> Integer #

Real a => Real (Shrink2 a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods toRational :: Shrink2 a -> Rational #
Show a => Show (Shrink2 a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> Shrink2 a -> ShowS # show :: Shrink2 a -> String # showList :: [Shrink2 a] -> ShowS #
Eq a => Eq (Shrink2 a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: Shrink2 a -> Shrink2 a -> Bool # (/=) :: Shrink2 a -> Shrink2 a -> Bool #
Ord a => Ord (Shrink2 a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods compare :: Shrink2 a -> Shrink2 a -> Ordering # (<) :: Shrink2 a -> Shrink2 a -> Bool # (<=) :: Shrink2 a -> Shrink2 a -> Bool # (>) :: Shrink2 a -> Shrink2 a -> Bool # (>=) :: Shrink2 a -> Shrink2 a -> Bool # max :: Shrink2 a -> Shrink2 a -> Shrink2 a # min :: Shrink2 a -> Shrink2 a -> Shrink2 a #

data Shrinking s a #

`Shrinking _ x`: allows for maintaining a state during shrinking.

Constructors

Shrinking s a |

#### Instances

Instances details

Functor (Shrinking s) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods fmap :: (a -> b) -> Shrinking s a -> Shrinking s b # (<$) :: a -> Shrinking s b -> Shrinking s a #
(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] #
Show a => Show (Shrinking s a) # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> Shrinking s a -> ShowS # show :: Shrinking s a -> String # showList :: [Shrinking s a] -> ShowS #

class ShrinkState s a where #

Methods

shrinkInit :: a -> s #

shrinkState :: a -> s -> [(a, s)] #

newtype ASCIIString #

`ASCIIString`: generates an ASCII string.

Constructors

ASCIIString |

Fields

- getASCIIString :: String

#### Instances

Instances details

Arbitrary ASCIIString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen ASCIIString # shrink :: ASCIIString -> [ASCIIString] #
Read ASCIIString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS ASCIIString # readList :: ReadS [ASCIIString] # readPrec :: ReadPrec ASCIIString # readListPrec :: ReadPrec [ASCIIString] #
Show ASCIIString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> ASCIIString -> ShowS # show :: ASCIIString -> String # showList :: [ASCIIString] -> ShowS #
Eq ASCIIString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: ASCIIString -> ASCIIString -> Bool # (/=) :: ASCIIString -> ASCIIString -> Bool #
Ord ASCIIString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods compare :: ASCIIString -> ASCIIString -> Ordering # (<) :: ASCIIString -> ASCIIString -> Bool # (<=) :: ASCIIString -> ASCIIString -> Bool # (>) :: ASCIIString -> ASCIIString -> Bool # (>=) :: ASCIIString -> ASCIIString -> Bool # max :: ASCIIString -> ASCIIString -> ASCIIString # min :: ASCIIString -> ASCIIString -> ASCIIString #

newtype UnicodeString #

`UnicodeString`: generates a unicode String. The string will not contain surrogate pairs.

Constructors

UnicodeString |

Fields

- getUnicodeString :: String

#### Instances

Instances details

Arbitrary UnicodeString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen UnicodeString # shrink :: UnicodeString -> [UnicodeString] #
Read UnicodeString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS UnicodeString # readList :: ReadS [UnicodeString] # readPrec :: ReadPrec UnicodeString # readListPrec :: ReadPrec [UnicodeString] #
Show UnicodeString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> UnicodeString -> ShowS # show :: UnicodeString -> String # showList :: [UnicodeString] -> ShowS #
Eq UnicodeString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: UnicodeString -> UnicodeString -> Bool # (/=) :: UnicodeString -> UnicodeString -> Bool #
Ord UnicodeString # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

compare :: UnicodeString -> UnicodeString -> Ordering #

(<) :: UnicodeString -> UnicodeString -> Bool #

(<=) :: UnicodeString -> UnicodeString -> Bool #

(>) :: UnicodeString -> UnicodeString -> Bool #

(>=) :: UnicodeString -> UnicodeString -> Bool #

max :: UnicodeString -> UnicodeString -> UnicodeString #

min :: UnicodeString -> UnicodeString -> UnicodeString #

newtype PrintableString #

`PrintableString`: generates a printable unicode String. The string will not contain surrogate pairs.

Constructors

PrintableString |

Fields

- getPrintableString :: String

#### Instances

Instances details

Arbitrary PrintableString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods arbitrary :: Gen PrintableString # shrink :: PrintableString -> [PrintableString] #
Read PrintableString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods readsPrec :: Int -> ReadS PrintableString # readList :: ReadS [PrintableString] # readPrec :: ReadPrec PrintableString # readListPrec :: ReadPrec [PrintableString] #
Show PrintableString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods showsPrec :: Int -> PrintableString -> ShowS # show :: PrintableString -> String # showList :: [PrintableString] -> ShowS #
Eq PrintableString # |
Instance details Defined in Test.QuickCheck.Modifiers Methods (==) :: PrintableString -> PrintableString -> Bool # (/=) :: PrintableString -> PrintableString -> Bool #
Ord PrintableString # |

Instance details

Defined in Test.QuickCheck.Modifiers

Methods

compare :: PrintableString -> PrintableString -> Ordering #

(<) :: PrintableString -> PrintableString -> Bool #

(<=) :: PrintableString -> PrintableString -> Bool #

(>) :: PrintableString -> PrintableString -> Bool #

(>=) :: PrintableString -> PrintableString -> Bool #

max :: PrintableString -> PrintableString -> PrintableString #

min :: PrintableString -> PrintableString -> PrintableString #

# Property combinators

data Property #

The type of properties.

#### Instances

Instances details

Testable Property # |
Instance details Defined in Test.QuickCheck.Property Methods property :: Property -> Property # propertyForAllShrinkShow :: Gen a -> (a -> [a]) -> (a -> [String]) -> (a -> Property) -> Property #

class Testable prop where #

The class of properties, i.e., types which QuickCheck knows how to test. Typically a property will be a function returning `Bool` or `Property`.

Minimal complete definition

property

Methods

property :: prop -> Property #

Convert the thing to a property.

propertyForAllShrinkShow :: Gen a -> (a -> [a]) -> (a -> [String]) -> (a -> prop) -> Property #

Optional; used internally in order to improve shrinking. Tests a property but also quantifies over an extra value (with a custom shrink and show function). The `Testable` instance for functions defines `propertyForAllShrinkShow` in a way that improves shrinking.

#### Instances

Instances details

Testable Discard # |
Instance details Defined in Test.QuickCheck.Property Methods property :: Discard -> Property # propertyForAllShrinkShow :: Gen a -> (a -> [a]) -> (a -> [String]) -> (a -> Discard) -> Property #
Testable Property # |
Instance details Defined in Test.QuickCheck.Property Methods property :: Property -> Property # propertyForAllShrinkShow :: Gen a -> (a -> [a]) -> (a -> [String]) -> (a -> Property) -> Property #
Testable () # |
Instance details Defined in Test.QuickCheck.Property Methods property :: () -> Property # propertyForAllShrinkShow :: Gen a -> (a -> [a]) -> (a -> [String]) -> (a -> ()) -> Property #
Testable Bool # |
Instance details Defined in Test.QuickCheck.Property Methods property :: Bool -> Property # propertyForAllShrinkShow :: Gen a -> (a -> [a]) -> (a -> [String]) -> (a -> Bool) -> Property #
Testable prop => Testable (Gen prop) # |
Instance details Defined in Test.QuickCheck.Property Methods property :: Gen prop -> Property # propertyForAllShrinkShow :: Gen a -> (a -> [a]) -> (a -> [String]) -> (a -> Gen prop) -> Property #
Testable prop => Testable (Maybe prop) # |
Instance details Defined in Test.QuickCheck.Property Methods property :: Maybe prop -> Property # propertyForAllShrinkShow :: Gen a -> (a -> [a]) -> (a -> [String]) -> (a -> Maybe prop) -> Property #
(Arbitrary a, Show a, Testable prop) => Testable (a -> prop) # |
Instance details Defined in Test.QuickCheck.Property Methods property :: (a -> prop) -> Property # propertyForAllShrinkShow :: Gen a0 -> (a0 -> [a0]) -> (a0 -> [String]) -> (a0 -> a -> prop) -> Property #

forAll :: (Show a, Testable prop) => Gen a -> (a -> prop) -> Property #

Explicit universal quantification: uses an explicitly given test case generator.

forAllShrink :: (Show a, Testable prop) => Gen a -> (a -> [a]) -> (a -> prop) -> Property #

Like `forAll`, but tries to shrink the argument for failing test cases.

forAllShow :: Testable prop => Gen a -> (a -> String) -> (a -> prop) -> Property #

Like `forAll`, but with an explicitly given show function.

forAllShrinkShow :: Testable prop => Gen a -> (a -> [a]) -> (a -> String) -> (a -> prop) -> Property #

Like `forAllShrink`, but with an explicitly given show function.

forAllBlind :: Testable prop => Gen a -> (a -> prop) -> Property #

Like `forAll`, but without printing the generated value.

forAllShrinkBlind :: Testable prop => Gen a -> (a -> [a]) -> (a -> prop) -> Property #

Like `forAllShrink`, but without printing the generated value.

shrinking #

Arguments

:: Testable prop |
=> (a -> [a]) | `shrink`-like function.
-> a | The original argument
-> (a -> prop) |
-> Property |

Shrinks the argument to a property if it fails. Shrinking is done automatically for most types. This function is only needed when you want to override the default behavior.

(==>) :: Testable prop => Bool -> prop -> Property infixr 0 #

Implication for properties: The resulting property holds if the first argument is `False` (in which case the test case is discarded), or if the given property holds. Note that using implication carelessly can severely skew test case distribution: consider using `cover` to make sure that your test data is still good quality.

data Discard #

If a property returns `Discard`, the current test case is discarded, the same as if a precondition was false.

An example is the definition of `==>`:

    (==>) :: Testable prop => Bool -> prop -> Property
    False ==> _ = property Discard
    True  ==> p = property p

Constructors

Discard |

#### Instances

Instances details

Testable Discard # |
Instance details Defined in Test.QuickCheck.Property Methods property :: Discard -> Property # propertyForAllShrinkShow :: Gen a -> (a -> [a]) -> (a -> [String]) -> (a -> Discard) -> Property #

discard :: a #

A special error value. If a property evaluates `discard`, it causes QuickCheck to discard the current test case. This can be useful if you want to discard the current test case, but are somewhere you can't use `==>`, such as inside a generator.

(===) :: (Eq a, Show a) => a -> a -> Property infix 4 #

Like `==`, but prints a counterexample when it fails.

(=/=) :: (Eq a, Show a) => a -> a -> Property infix 4 #

Like `/=`, but prints a counterexample when it fails.

total :: NFData a => a -> Property #

Checks that a value is total, i.e., doesn't crash when evaluated.

ioProperty :: Testable prop => IO prop -> Property #

Do I/O inside a property.

Warning: any random values generated inside of the argument to `ioProperty` will not currently be shrunk. For best results, generate all random values before calling `ioProperty`, or use `idempotentIOProperty` if that is safe.

idempotentIOProperty :: Testable prop => IO prop -> Property #

Do I/O inside a property.

Warning: during shrinking, the I/O may not always be re-executed. Instead, the I/O may be executed once and then its result retained. If this is not acceptable, use `ioProperty` instead.

## Controlling property execution

verbose :: Testable prop => prop -> Property #

Prints out the generated test case every time the property is tested. Only variables quantified over inside the `verbose` are printed.

Note: for technical reasons, the test case is printed out after the property is tested. To debug a property that goes into an infinite loop, use `within` to add a timeout instead.

verboseShrinking :: Testable prop => prop -> Property #

Prints out the generated test case every time the property fails, including during shrinking. Only variables quantified over inside the `verboseShrinking` are printed.

Note: for technical reasons, the test case is printed out after the property is tested. To debug a property that goes into an infinite loop, use `within` to add a timeout instead.

noShrinking :: Testable prop => prop -> Property #

Disables shrinking for a property altogether. Only quantification inside the call to `noShrinking` is affected.

withMaxSuccess :: Testable prop => Int -> prop -> Property #

Configures how many times a property will be tested.

For example,

    quickCheck (withMaxSuccess 1000 p)

will test `p` up to 1000 times.

within :: Testable prop => Int -> prop -> Property #

Considers a property failed if it does not complete within the given number of microseconds.

Note: if the property times out, variables quantified inside the `within` will not be printed. Therefore, you should use `within` only in the body of your property.

Good: `prop_foo a b c = within 1000000 ...`

Bad: `prop_foo = within 1000000 $ \a b c -> ...`

Bad: `prop_foo a b c = ...; main = quickCheck (within 1000000 prop_foo)`

discardAfter :: Testable prop => Int -> prop -> Property #

Discards the test case if it does not complete within the given number of microseconds. This can be useful when testing algorithms that have pathological cases where they run extremely slowly.

withDiscardRatio :: Testable prop => Int -> prop -> Property #

Configures how many times a property is allowed to be discarded before failing.

For example,

    quickCheck (withDiscardRatio 10 p)

will allow `p` to fail up to 10 times per successful test.

withMaxSize :: Testable prop => Int -> prop -> Property #

Configure the maximum size a property will be tested at.

withMaxShrinks :: Testable prop => Int -> prop -> Property #

Configure the maximum number of times a property will be shrunk.

For example,

    quickCheck (withMaxShrinks 100 p)

will cause `p` to only attempt 100 shrinks on failure.

once :: Testable prop => prop -> Property #

Modifies a property so that it only will be tested once. Opposite of `again`.

again :: Testable prop => prop -> Property #

Modifies a property so that it will be tested repeatedly. Opposite of `once`.

mapSize :: Testable prop => (Int -> Int) -> prop -> Property #

Adjust the test case size for a property, by transforming it with the given function.

## Conjunction and disjunction

(.&.) :: (Testable prop1, Testable prop2) => prop1 -> prop2 -> Property infixr 1 #

Nondeterministic choice: `p1` `.&.` `p2` picks randomly one of `p1` and `p2` to test. If you test the property 100 times it makes 100 random choices.

(.&&.) :: (Testable prop1, Testable prop2) => prop1 -> prop2 -> Property infixr 1 #

Conjunction: `p1` `.&&.` `p2` passes if both `p1` and `p2` pass.

conjoin :: Testable prop => [prop] -> Property #

Take the conjunction of several properties.

(.||.) :: (Testable prop1, Testable prop2) => prop1 -> prop2 -> Property infixr 1 #

Disjunction: `p1` `.||.` `p2` passes unless `p1` and `p2` simultaneously fail.

disjoin :: Testable prop => [prop] -> Property #

Take the disjunction of several properties.

## What to do on failure

data Witness #

Constructors

(Typeable a, Show a) => Wit a |

#### Instances

Instances details

Show Witness # |
Instance details Defined in Test.QuickCheck.Property Methods showsPrec :: Int -> Witness -> ShowS # show :: Witness -> String # showList :: [Witness] -> ShowS #

witness :: (Typeable a, Show a, Testable prop) => a -> prop -> Property #

Return a value in the `witnesses` field of the `Result` returned by `quickCheckResult`. Witnesses are returned outer-most first.

In ghci, for example:

    >>> [Wit x] <- fmap witnesses . quickCheckResult $ \ x -> witness x $ x == (0 :: Int)
    *** Failed! Falsified (after 2 tests):
    1
    >>> x
    1
    >>> :t x
    x :: Int

coerceWitness :: Typeable a => Witness -> a #

castWitness :: Typeable a => Witness -> Maybe a #

counterexample :: Testable prop => String -> prop -> Property #

Adds the given string to the counterexample if the property fails.

printTestCase :: Testable prop => String -> prop -> Property #

Deprecated: Use counterexample instead

Adds the given string to the counterexample if the property fails.

whenFail :: Testable prop => IO () -> prop -> Property #

Performs an `IO` action after the last failure of a property.

whenFail' :: Testable prop => IO () -> prop -> Property #

Performs an `IO` action every time a property fails. Thus, if shrinking is done, this can be used to keep track of the failures along the way.

expectFailure :: Testable prop => prop -> Property #

Indicates that a property is supposed to fail. QuickCheck will report an error if it does not fail.

# Analysing test case distribution

label :: Testable prop => String -> prop -> Property #

Attaches a label to a test case. This is used for reporting test case distribution.

For example:

    prop_reverse_reverse :: [Int] -> Property
    prop_reverse_reverse xs =
      label ("length of input is " ++ show (length xs)) $
        reverse (reverse xs) === xs

    >>> quickCheck prop_reverse_reverse
    +++ OK, passed 100 tests:
    7% length of input is 7
    6% length of input is 3
    5% length of input is 4
    4% length of input is 6
    ...

Each use of `label` in your property results in a separate table of test case distribution in the output. If this is not what you want, use `tabulate`.

collect :: (Show a, Testable prop) => a -> prop -> Property #

Attaches a label to a test case. This is used for reporting test case distribution.

    collect x = label (show x)

For example:

    prop_reverse_reverse :: [Int] -> Property
    prop_reverse_reverse xs =
      collect (length xs) $
        reverse (reverse xs) === xs

    >>> quickCheck prop_reverse_reverse
    +++ OK, passed 100 tests:
    7% 7
    6% 3
    5% 4
    4% 6
    ...

Each use of `collect` in your property results in a separate table of test case distribution in the output. If this is not what you want, use `tabulate`.

classify #

Arguments

:: Testable prop |
=> Bool | `True` if the test case should be labelled.
-> String | Label.
-> prop |
-> Property |

Reports how many test cases satisfy a given condition.

For example:

    prop_sorted_sort :: [Int] -> Property
    prop_sorted_sort xs =
      sorted xs ==>
      classify (length xs > 1) "non-trivial" $
      sort xs === xs

    >>> quickCheck prop_sorted_sort
    +++ OK, passed 100 tests (22% non-trivial).

tabulate :: Testable prop => String -> [String] -> prop -> Property #

Collects information about test case distribution into a table. The arguments to `tabulate` are the table's name and a list of values associated with the current test case. After testing, QuickCheck prints the frequency of all collected values. The frequencies are expressed as a percentage of the total number of values collected.

You should prefer `tabulate` to `label` when each test case is associated with a varying number of values. Here is a (not terribly useful) example, where the test data is a list of integers and we record all values that occur in the list:

    prop_sorted_sort :: [Int] -> Property
    prop_sorted_sort xs =
      sorted xs ==>
      tabulate "List elements" (map show xs) $
      sort xs === xs

    >>> quickCheck prop_sorted_sort
    +++ OK, passed 100 tests; 1684 discarded.

    List elements (109 in total):
     3.7% 0
     3.7% 17
     3.7% 2
     3.7% 6
     2.8% -6
     2.8% -7

Here is a more useful example. We are testing a chatroom, where the user can log in, log out, or send a message:

    data Command = LogIn | LogOut | SendMessage String deriving (Data, Show)
    instance Arbitrary Command where ...

There are some restrictions on command sequences; for example, the user must log in before doing anything else. The function `valid :: [Command] -> Bool` checks that a command sequence is allowed. Our property then has the form:

    prop_chatroom :: [Command] -> Property
    prop_chatroom cmds =
      valid cmds ==>
        ...

The use of `==>` may skew test case distribution. We use `collect` to see the length of the command sequences, and `tabulate` to get the frequencies of the individual commands:

    prop_chatroom :: [Command] -> Property
    prop_chatroom cmds =
      wellFormed cmds LoggedOut ==>
      'collect' (length cmds) $
      'tabulate' "Commands" (map (show . 'Data.Data.toConstr') cmds) $
        ...

    >>> quickCheckWith stdArgs{maxDiscardRatio = 1000} prop_chatroom
    +++ OK, passed 100 tests; 2775 discarded:
    60% 0
    20% 1
    15% 2
     3% 3
     1% 4
     1% 5

    Commands (68 in total):
    62% LogIn
    22% SendMessage
    16% LogOut

## Checking test case distribution

cover #

Arguments

:: Testable prop |
=> Double | The required percentage (0-100) of test cases.
-> Bool | `True` if the test case belongs to the class.
-> String | Label for the test case class.
-> prop |
-> Property |

Checks that at least the given proportion of successful test cases belong to the given class. Discarded tests (i.e. ones with a false precondition) do not affect coverage.

Note: If the coverage check fails, QuickCheck prints out a warning, but the property does not fail. To make the property fail, use `checkCoverage`.

For example:

    prop_sorted_sort :: [Int] -> Property
    prop_sorted_sort xs =
      sorted xs ==>
      cover 50 (length xs > 1) "non-trivial" $
      sort xs === xs

    >>> quickCheck prop_sorted_sort
    +++ OK, passed 100 tests; 135 discarded (26% non-trivial).

    Only 26% non-trivial, but expected 50%

coverTable :: Testable prop => String -> [(String, Double)] -> prop -> Property #

Checks that the values in a given `table` appear a certain proportion of the time. A call to `coverTable` `table` `[(x1, p1), ..., (xn, pn)]` asserts that of the values in `table`, `x1` should appear at least `p1` percent of the time that `table` appears, `x2` at least `p2` percent of the time that `table` appears, and so on.

Note: If the coverage check fails, QuickCheck prints out a warning, but the property does not fail. To make the property fail, use `checkCoverage`.

Continuing the example from the `tabular` combinator...

    data Command = LogIn | LogOut | SendMessage String deriving (Data, Show)
    prop_chatroom :: [Command] -> Property
    prop_chatroom cmds =
      wellFormed cmds LoggedOut ==>
      'tabulate' "Commands" (map (show . 'Data.Data.toConstr') cmds) $
        ...

...we can add a coverage requirement as follows, which checks that `LogIn`, `LogOut` and `SendMessage` each occur at least 25% of the time:

    prop_chatroom :: [Command] -> Property
    prop_chatroom cmds =
      wellFormed cmds LoggedOut ==>
      coverTable "Commands" [("LogIn", 25), ("LogOut", 25), ("SendMessage", 25)] $
      'tabulate' "Commands" (map (show . 'Data.Data.toConstr') cmds) $
        ... property goes here ...

    >>> quickCheck prop_chatroom
    +++ OK, passed 100 tests; 2909 discarded:
    56% 0
    17% 1
    10% 2
     6% 3
     5% 4
     3% 5
     3% 7

    Commands (111 in total):
    51.4% LogIn
    30.6% SendMessage
    18.0% LogOut

    Table 'Commands' had only 18.0% LogOut, but expected 25.0%

checkCoverage :: Testable prop => prop -> Property #

Check that all coverage requirements defined by `cover` and `coverTable` are met, using a statistically sound test, and fail if they are not met.

Ordinarily, a failed coverage check does not cause the property to fail. This is because the coverage requirement is not tested in a statistically sound way. If you use `cover` to express that a certain value must appear 20% of the time, QuickCheck will warn you if the value only appears in 19 out of 100 test cases - but since the coverage varies randomly, you may have just been unlucky, and there may not be any real problem with your test generation.

When you use `checkCoverage`, QuickCheck uses a statistical test to account for the role of luck in coverage failures. It will run as many tests as needed until it is sure about whether the coverage requirements are met. If a coverage requirement is not met, the property fails.

Example:

    quickCheck (checkCoverage prop_foo)

checkCoverageWith :: Testable prop => Confidence -> prop -> Property #

Check coverage requirements using a custom confidence level. See `stdConfidence`.

An example of making the statistical test less stringent in order to improve performance:

    quickCheck (checkCoverageWith stdConfidence{certainty = 10^6} prop_foo)

data Confidence #

The statistical parameters used by `checkCoverage`.

Constructors

Confidence |

Fields

- certainty :: Integer

  How certain `checkCoverage` must be before the property fails. If the coverage requirement is met, and the certainty parameter is `n`, then you should get a false positive at most one in `n` runs of QuickCheck. The default value is `10^9`.

  Lower values will speed up `checkCoverage` at the cost of false positives.

  If you are using `checkCoverage` as part of a test suite, you should be careful not to set `certainty` too low. If you want, say, a 1% chance of a false positive during a project's lifetime, then `certainty` should be set to at least `100 * m * n`, where `m` is the number of uses of `cover` in the test suite, and `n` is the number of times you expect the test suite to be run during the project's lifetime. The default value is chosen to be big enough for most projects.

- tolerance :: Double

  For statistical reasons, `checkCoverage` will not reject coverage levels that are only slightly below the required levels. If the required level is `p` then an actual level of `tolerance * p` will be accepted. The default value is `0.9`.

  Lower values will speed up `checkCoverage` at the cost of not detecting minor coverage violations.

#### Instances

Instances details

Show Confidence # |
Instance details Defined in Test.QuickCheck.State Methods showsPrec :: Int -> Confidence -> ShowS # show :: Confidence -> String # showList :: [Confidence] -> ShowS #

stdConfidence :: Confidence #

The standard parameters used by `checkCoverage`: `certainty = 10^9`, `tolerance = 0.9`. See `Confidence` for the meaning of the parameters.

## Generating example test cases

labelledExamples :: Testable prop => prop -> IO () #

Given a property, which must use `label`, `collect`, `classify` or `cover` to associate labels with test cases, find an example test case for each possible label. The example test cases are minimised using shrinking.

For example, suppose we test ``delete` x xs` and record the number of times that `x` occurs in `xs`:

    prop_delete :: Int -> [Int] -> Property
    prop_delete x xs =
      classify (count x xs == 0) "count x xs == 0" $
      classify (count x xs == 1) "count x xs == 1" $
      classify (count x xs >= 2) "count x xs >= 2" $
      counterexample (show (delete x xs)) $
      count x (delete x xs) == max 0 (count x xs-1)
      where count x xs = length (filter (== x) xs)

`labelledExamples` generates three example test cases, one for each label:

    >>> labelledExamples prop_delete
    *** Found example of count x xs == 0
    0
    []
    []

    *** Found example of count x xs == 1
    0
    [0]
    []

    *** Found example of count x xs >= 2
    5
    [5,5]
    [5]

    +++ OK, passed 100 tests:
    78% count x xs == 0
    21% count x xs == 1
     1% count x xs >= 2

labelledExamplesWith :: Testable prop => Args -> prop -> IO () #

A variant of `labelledExamples` that takes test arguments.

labelledExamplesWithResult :: Testable prop => Args -> prop -> IO Result #

A variant of `labelledExamples` that takes test arguments and returns a result.

labelledExamplesResult :: Testable prop => prop -> IO Result #

A variant of `labelledExamples` that returns a result.