QuickCheck-2.14.2: Automatic testing of Haskell programs
Safe Haskell Safe
Language Haskell2010

Test.QuickCheck

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.

Synopsis

Running tests

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

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 Source #

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 before giving up. Setting this to zero turns shrinking off.

data Result Source #

Result represents the test result

Constructors

Success

A successful test run

Fields

GaveUp

Given up

Fields

Failure

A failed test run

Fields

NoExpectedFailure

A property that should have failed did not

Fields

stdArgs :: Args Source #

The default test arguments

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

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

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

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

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

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

isSuccess :: Result -> Bool Source #

Check if the test run result was a success

Running tests verbosely

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

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 () Source #

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 Source #

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 Source #

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 Source #

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 Source #

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 Source #

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 Source #

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 Source #

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 Source #

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 Source #

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 Source #

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 Source #

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] Source #

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

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

Most implementations of shrink should try at least three things:

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

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

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

We can then define shrink as follows:

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

There are a couple of subtleties here:

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

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

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

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

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

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

Instances

Instances details
Arbitrary Bool Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Char Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Double Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Float Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Int Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Int8 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Int16 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Int32 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Int64 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Integer Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Ordering Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Word Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Word8 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Word16 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Word32 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Word64 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary () Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Version Source #

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

Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary ExitCode Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary All Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary Any Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CChar Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CSChar Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CUChar Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CShort Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CUShort Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CInt Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CUInt Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CLong Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CULong Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CLLong Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CULLong Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CFloat Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CDouble Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CPtrdiff Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CSize Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CWchar Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CSigAtomic Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CClock Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CTime Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CUSeconds Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CSUSeconds Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CIntPtr Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CUIntPtr Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CIntMax Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary CUIntMax Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary IntSet Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary OrdC Source #
Instance details

Defined in Test.QuickCheck.Poly

Arbitrary OrdB Source #
Instance details

Defined in Test.QuickCheck.Poly

Arbitrary OrdA Source #
Instance details

Defined in Test.QuickCheck.Poly

Arbitrary C Source #
Instance details

Defined in Test.QuickCheck.Poly

Arbitrary B Source #
Instance details

Defined in Test.QuickCheck.Poly

Arbitrary A Source #
Instance details

Defined in Test.QuickCheck.Poly

Arbitrary PrintableString Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary UnicodeString Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary ASCIIString Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary a => Arbitrary [a] Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( Maybe a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Integral a => Arbitrary ( Ratio a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( Complex a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( ZipList a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( Identity a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( First a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( Last a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( Dual a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( Sum a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( Product a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( IntMap a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( Tree a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( Seq a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary ( Smart a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary a => Arbitrary ( Shrink2 a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Integral a => Arbitrary ( Small a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

Arbitrary a => Arbitrary ( InfiniteList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary a => Arbitrary ( NonEmptyList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

Arbitrary a => Arbitrary ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary a => Arbitrary ( Blind a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Arbitrary

Methods

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

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

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

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

Methods

arbitrary :: Gen (a, b) Source #

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

HasResolution a => Arbitrary ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Function

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

Defined in Test.QuickCheck.Function

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

Defined in Test.QuickCheck.Arbitrary

Methods

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

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

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

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

Methods

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

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

( Arbitrary1 f, Arbitrary1 g, Arbitrary a) => Arbitrary ( Product f g a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

Methods

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

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

( Arbitrary1 f, Arbitrary1 g, Arbitrary a) => Arbitrary ( Compose f g a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

Methods

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

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

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

Defined in Test.QuickCheck.Arbitrary

Methods

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

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

( 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) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

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

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

( 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) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

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

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

( 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) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

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

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

Helper functions for implementing shrink

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

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

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

All immediate subterms of a term.

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

Recursively shrink all immediate subterms.

shrinkNothing :: a -> [a] Source #

Returns no shrinking alternatives.

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

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

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

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] Source #

Non-overloaded version of shrinkMap .

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

Shrink an integral number.

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

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

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

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 where Source #

Lifting of the Arbitrary class to unary type constructors.

Minimal complete definition

liftArbitrary

Methods

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

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

Instances

Instances details
Arbitrary1 [] Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

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

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

Arbitrary1 Maybe Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary1 ZipList Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary1 Identity Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary1 IntMap Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary1 Tree Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary1 Seq Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary1 ( Either a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary1 ( (,) a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

liftArbitrary :: Gen a0 -> Gen (a, a0) Source #

liftShrink :: (a0 -> [a0]) -> (a, a0) -> [(a, a0)] Source #

( Ord k, Arbitrary k) => Arbitrary1 ( Map k) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary1 ( Const a :: Type -> Type ) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Arbitrary a => Arbitrary1 ( Constant a :: Type -> Type ) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => Arbitrary1 ((->) a :: Type -> Type ) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

liftArbitrary :: Gen a0 -> Gen (a -> a0) Source #

liftShrink :: (a0 -> [a0]) -> (a -> a0) -> [a -> a0] Source #

( Arbitrary1 f, Arbitrary1 g) => Arbitrary1 ( Product f g) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

( Arbitrary1 f, Arbitrary1 g) => Arbitrary1 ( Compose f g) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

class Arbitrary2 f where Source #

Lifting of the Arbitrary class to binary type constructors.

Minimal complete definition

liftArbitrary2

Methods

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

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

The Gen monad: combinators for building random generators

data Gen a Source #

A generator for values of type a .

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

Generator combinators

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

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

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

A fast implementation of choose for bounded integral types.

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

A fast implementation of choose for enumerated types.

chooseAny :: Random a => Gen a Source #

Generates a random element over the natural range of a .

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

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

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

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

elements :: [a] -> Gen a Source #

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

growingElements :: [a] -> Gen a Source #

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

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

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 Source #

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 :: Int -> Gen a -> Gen a Source #

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

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

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

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

Generates a value that satisfies a predicate.

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

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

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

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 Source #

Apply a binary function to random arguments.

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

Apply a ternary function to random arguments.

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

Apply a function of arity 4 to random arguments.

Generators for lists

listOf :: Gen a -> Gen [a] Source #

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

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

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

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

Generates a list of the given length.

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

Generates a list of a given length.

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

Generates an infinite list.

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

Generates an infinite list.

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

Generates a random permutation of the given list.

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

Generates a random subsequence of the given list.

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

Generates an ordered list.

Generators for particular types

arbitrarySizedIntegral :: Integral a => Gen a Source #

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 Source #

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

arbitrarySizedFractional :: Fractional a => Gen a Source #

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 Source #

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 Source #

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 Source #

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 Source #

Generates an element of a bounded enumeration.

arbitraryUnicodeChar :: Gen Char Source #

Generates any Unicode character (but not a surrogate)

arbitraryASCIIChar :: Gen Char Source #

Generates a random ASCII character (0-127).

arbitraryPrintableChar :: Gen Char Source #

Generates a printable Unicode character.

Running generators

generate :: Gen a -> IO a Source #

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

Debugging generators

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

Generates some example values and prints them to stdout .

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

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 Source #

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)

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

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 Source #

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 Source #

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

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

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 Source #

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 Source #

A modifier for testing ternary functions.

class Function a where Source #

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 Source #

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

Instances

Instances details
Function Bool Source #
Instance details

Defined in Test.QuickCheck.Function

Function Char Source #
Instance details

Defined in Test.QuickCheck.Function

Function Double Source #
Instance details

Defined in Test.QuickCheck.Function

Function Float Source #
Instance details

Defined in Test.QuickCheck.Function

Function Int Source #
Instance details

Defined in Test.QuickCheck.Function

Function Int8 Source #
Instance details

Defined in Test.QuickCheck.Function

Function Int16 Source #
Instance details

Defined in Test.QuickCheck.Function

Function Int32 Source #
Instance details

Defined in Test.QuickCheck.Function

Function Int64 Source #
Instance details

Defined in Test.QuickCheck.Function

Function Integer Source #
Instance details

Defined in Test.QuickCheck.Function

Function Ordering Source #
Instance details

Defined in Test.QuickCheck.Function

Function Word Source #
Instance details

Defined in Test.QuickCheck.Function

Function Word8 Source #
Instance details

Defined in Test.QuickCheck.Function

Function Word16 Source #
Instance details

Defined in Test.QuickCheck.Function

Function Word32 Source #
Instance details

Defined in Test.QuickCheck.Function

Function Word64 Source #
Instance details

Defined in Test.QuickCheck.Function

Function () Source #
Instance details

Defined in Test.QuickCheck.Function

Methods

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

Function All Source #
Instance details

Defined in Test.QuickCheck.Function

Function Any Source #
Instance details

Defined in Test.QuickCheck.Function

Function IntSet Source #
Instance details

Defined in Test.QuickCheck.Function

Function OrdC Source #
Instance details

Defined in Test.QuickCheck.Function

Function OrdB Source #
Instance details

Defined in Test.QuickCheck.Function

Function OrdA Source #
Instance details

Defined in Test.QuickCheck.Function

Function C Source #
Instance details

Defined in Test.QuickCheck.Function

Function B Source #
Instance details

Defined in Test.QuickCheck.Function

Function A Source #
Instance details

Defined in Test.QuickCheck.Function

Function a => Function [a] Source #
Instance details

Defined in Test.QuickCheck.Function

Methods

function :: ([a] -> b) -> [a] :-> b Source #

Function a => Function ( Maybe a) Source #
Instance details

Defined in Test.QuickCheck.Function

( Integral a, Function a) => Function ( Ratio a) Source #
Instance details

Defined in Test.QuickCheck.Function

( RealFloat a, Function a) => Function ( Complex a) Source #
Instance details

Defined in Test.QuickCheck.Function

Function a => Function ( Identity a) Source #
Instance details

Defined in Test.QuickCheck.Function

Function a => Function ( First a) Source #
Instance details

Defined in Test.QuickCheck.Function

Function a => Function ( Last a) Source #
Instance details

Defined in Test.QuickCheck.Function

Function a => Function ( Dual a) Source #
Instance details

Defined in Test.QuickCheck.Function

Function a => Function ( Sum a) Source #
Instance details

Defined in Test.QuickCheck.Function

Function a => Function ( Product a) Source #
Instance details

Defined in Test.QuickCheck.Function

Function a => Function ( IntMap a) Source #
Instance details

Defined in Test.QuickCheck.Function

Function a => Function ( Tree a) Source #
Instance details

Defined in Test.QuickCheck.Function

Function a => Function ( Seq a) Source #
Instance details

Defined in Test.QuickCheck.Function

( Ord a, Function a) => Function ( Set a) Source #
Instance details

Defined in Test.QuickCheck.Function

( Function a, Function b) => Function ( Either a b) Source #
Instance details

Defined in Test.QuickCheck.Function

Methods

function :: ( Either a b -> b0) -> Either a b :-> b0 Source #

( Function a, Function b) => Function (a, b) Source #
Instance details

Defined in Test.QuickCheck.Function

Methods

function :: ((a, b) -> b0) -> (a, b) :-> b0 Source #

HasResolution a => Function ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Function

( Ord a, Function a, Function b) => Function ( Map a b) Source #
Instance details

Defined in Test.QuickCheck.Function

Methods

function :: ( Map a b -> b0) -> Map a b :-> b0 Source #

( Function a, Function b, Function c) => Function (a, b, c) Source #
Instance details

Defined in Test.QuickCheck.Function

Methods

function :: ((a, b, c) -> b0) -> (a, b, c) :-> b0 Source #

Function a => Function ( Const a b) Source #
Instance details

Defined in Test.QuickCheck.Function

Methods

function :: ( Const a b -> b0) -> Const a b :-> b0 Source #

Function (f a) => Function ( Alt f a) Source #
Instance details

Defined in Test.QuickCheck.Function

Methods

function :: ( Alt f a -> b) -> Alt f a :-> b Source #

( Function a, Function b, Function c, Function d) => Function (a, b, c, d) Source #
Instance details

Defined in Test.QuickCheck.Function

Methods

function :: ((a, b, c, d) -> b0) -> (a, b, c, d) :-> b0 Source #

( Function a, Function b, Function c, Function d, Function e) => Function (a, b, c, d, e) Source #
Instance details

Defined in Test.QuickCheck.Function

Methods

function :: ((a, b, c, d, e) -> b0) -> (a, b, c, d, e) :-> b0 Source #

( Function a, Function b, Function c, Function d, Function e, Function f) => Function (a, b, c, d, e, f) Source #
Instance details

Defined in Test.QuickCheck.Function

Methods

function :: ((a, b, c, d, e, f) -> b0) -> (a, b, c, d, e, f) :-> b0 Source #

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

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

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 Source #

Provides a Function instance for types with Show and Read .

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

Provides a Function instance for types with Integral .

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

Provides a Function instance for types with RealFrac .

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

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 Source #

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 Source #

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 Source #

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 Source #

Instances

Instances details
CoArbitrary Bool Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Char Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Double Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Float Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Int Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Int8 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Int16 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Int32 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Int64 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Integer Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Ordering Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Word Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Word8 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Word16 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Word32 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Word64 Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary () Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Version Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary All Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary Any Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary IntSet Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary OrdC Source #
Instance details

Defined in Test.QuickCheck.Poly

CoArbitrary OrdB Source #
Instance details

Defined in Test.QuickCheck.Poly

CoArbitrary OrdA Source #
Instance details

Defined in Test.QuickCheck.Poly

CoArbitrary C Source #
Instance details

Defined in Test.QuickCheck.Poly

CoArbitrary B Source #
Instance details

Defined in Test.QuickCheck.Poly

CoArbitrary A Source #
Instance details

Defined in Test.QuickCheck.Poly

CoArbitrary a => CoArbitrary [a] Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( Maybe a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

( Integral a, CoArbitrary a) => CoArbitrary ( Ratio a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( Complex a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( ZipList a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( Identity a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( First a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( Last a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( Dual a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( Sum a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( Product a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( IntMap a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( Tree a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( Seq a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( Set a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

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

Defined in Test.QuickCheck.Arbitrary

Methods

coarbitrary :: (a -> b) -> Gen b0 -> Gen b0 Source #

( CoArbitrary a, CoArbitrary b) => CoArbitrary ( Either a b) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

( CoArbitrary a, CoArbitrary b) => CoArbitrary (a, b) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

coarbitrary :: (a, b) -> Gen b0 -> Gen b0 Source #

HasResolution a => CoArbitrary ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

( CoArbitrary k, CoArbitrary v) => CoArbitrary ( Map k v) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

( CoArbitrary a, CoArbitrary b, CoArbitrary c) => CoArbitrary (a, b, c) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

coarbitrary :: (a, b, c) -> Gen b0 -> Gen b0 Source #

CoArbitrary a => CoArbitrary ( Const a b) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary (f a) => CoArbitrary ( Alt f a) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

CoArbitrary a => CoArbitrary ( Constant a b) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

( CoArbitrary a, CoArbitrary b, CoArbitrary c, CoArbitrary d) => CoArbitrary (a, b, c, d) Source #
Instance details

Defined in Test.QuickCheck.Arbitrary

Methods

coarbitrary :: (a, b, c, d) -> Gen b0 -> Gen b0 Source #

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

Defined in Test.QuickCheck.Arbitrary

Methods

coarbitrary :: (a, b, c, d, e) -> Gen b0 -> Gen b0 Source #

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

Generic CoArbitrary implementation.

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

Modifies a generator using an integer seed.

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

A coarbitrary implementation for integral numbers.

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

A coarbitrary implementation for real numbers.

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

coarbitrary helper for lazy people :-).

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

A coarbitrary implementation for enums.

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

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 Source #

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

Constructors

Blind

Fields

Instances

Instances details
Functor Blind Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Enum a => Enum ( Blind a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( Blind a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Integral a => Integral ( Blind a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Num a => Num ( Blind a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( Blind a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Real a => Real ( Blind a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show ( Blind a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary a => Arbitrary ( Blind a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

newtype Fixed a Source #

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

Constructors

Fixed

Fields

Instances

Instances details
Functor Fixed Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Enum a => Enum ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Integral a => Integral ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Num a => Num ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read a => Read ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Real a => Real ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show a => Show ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary a => Arbitrary ( Fixed a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

newtype OrderedList a Source #

Ordered xs : guarantees that xs is ordered.

Constructors

Ordered

Fields

Instances

Instances details
Functor OrderedList Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( OrderedList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( OrderedList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read a => Read ( OrderedList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show a => Show ( OrderedList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

newtype NonEmptyList a Source #

NonEmpty xs : guarantees that xs is non-empty.

Constructors

NonEmpty

Fields

Instances

Instances details
Functor NonEmptyList Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( NonEmptyList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( NonEmptyList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read a => Read ( NonEmptyList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show a => Show ( NonEmptyList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary a => Arbitrary ( NonEmptyList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

data InfiniteList a Source #

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

newtype SortedList a Source #

Sorted xs : guarantees that xs is sorted.

Constructors

Sorted

Fields

Instances

Instances details
Functor SortedList Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( SortedList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( SortedList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read a => Read ( SortedList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show a => Show ( SortedList a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

newtype Positive a Source #

Positive x : guarantees that x > 0 .

Constructors

Positive

Fields

Instances

Instances details
Functor Positive Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Enum a => Enum ( Positive a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( Positive a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( Positive a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read a => Read ( Positive a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show a => Show ( Positive a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

newtype Negative a Source #

Negative x : guarantees that x < 0 .

Constructors

Negative

Fields

Instances

Instances details
Functor Negative Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Enum a => Enum ( Negative a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( Negative a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( Negative a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read a => Read ( Negative a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show a => Show ( Negative a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

newtype NonZero a Source #

NonZero x : guarantees that x /= 0 .

Constructors

NonZero

Fields

Instances

Instances details
Functor NonZero Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Enum a => Enum ( NonZero a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( NonZero a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( NonZero a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read a => Read ( NonZero a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show a => Show ( NonZero a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

newtype NonNegative a Source #

NonNegative x : guarantees that x >= 0 .

Constructors

NonNegative

Fields

Instances

Instances details
Functor NonNegative Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Enum a => Enum ( NonNegative a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( NonNegative a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( NonNegative a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read a => Read ( NonNegative a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show a => Show ( NonNegative a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

newtype NonPositive a Source #

NonPositive x : guarantees that x <= 0 .

Constructors

NonPositive

Fields

Instances

Instances details
Functor NonPositive Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Enum a => Enum ( NonPositive a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( NonPositive a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( NonPositive a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read a => Read ( NonPositive a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show a => Show ( NonPositive a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

newtype Large a Source #

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

Instances

Instances details
Functor Large Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Enum a => Enum ( Large a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( Large a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Integral a => Integral ( Large a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Num a => Num ( Large a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( Large a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read a => Read ( Large a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Real a => Real ( Large a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show a => Show ( Large a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ix a => Ix ( Large a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

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

Defined in Test.QuickCheck.Modifiers

newtype Small a Source #

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

Constructors

Small

Fields

Instances

Instances details
Functor Small Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Enum a => Enum ( Small a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( Small a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Integral a => Integral ( Small a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Num a => Num ( Small a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( Small a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read a => Read ( Small a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Real a => Real ( Small a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show a => Show ( Small a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ix a => Ix ( Small a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Integral a => Arbitrary ( Small a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

newtype Shrink2 a Source #

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

Constructors

Shrink2

Fields

Instances

Instances details
Functor Shrink2 Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Enum a => Enum ( Shrink2 a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Eq a => Eq ( Shrink2 a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Integral a => Integral ( Shrink2 a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Num a => Num ( Shrink2 a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord a => Ord ( Shrink2 a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read a => Read ( Shrink2 a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Real a => Real ( Shrink2 a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show a => Show ( Shrink2 a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary a => Arbitrary ( Shrink2 a) Source #
Instance details

Defined in Test.QuickCheck.Modifiers

class ShrinkState s a where Source #

Methods

shrinkInit :: a -> s Source #

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

newtype UnicodeString Source #

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

newtype PrintableString Source #

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

Instances

Instances details
Eq PrintableString Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Ord PrintableString Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Read PrintableString Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Show PrintableString Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Arbitrary PrintableString Source #
Instance details

Defined in Test.QuickCheck.Modifiers

Property combinators

data Property Source #

The type of properties.

class Testable prop where Source #

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

If a property does no quantification, i.e. has no parameters and doesn't use forAll , it will only be tested once. This may not be what you want if your property is an IO Bool . You can change this behaviour using the again combinator.

Minimal complete definition

property

Methods

property :: prop -> Property Source #

Convert the thing to a property.

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

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 Bool Source #
Instance details

Defined in Test.QuickCheck.Property

Testable () Source #
Instance details

Defined in Test.QuickCheck.Property

Testable Discard Source #
Instance details

Defined in Test.QuickCheck.Property

Testable Property Source #
Instance details

Defined in Test.QuickCheck.Property

Testable prop => Testable ( Maybe prop) Source #
Instance details

Defined in Test.QuickCheck.Property

Testable prop => Testable ( Gen prop) Source #
Instance details

Defined in Test.QuickCheck.Property

( Arbitrary a, Show a, Testable prop) => Testable (a -> prop) Source #
Instance details

Defined in Test.QuickCheck.Property

Methods

property :: (a -> prop) -> Property Source #

propertyForAllShrinkShow :: Gen a0 -> (a0 -> [a0]) -> (a0 -> [ String ]) -> (a0 -> a -> prop) -> Property Source #

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

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

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

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

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

Like forAll , but with an explicitly given show function.

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

Like forAllShrink , but with an explicitly given show function.

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

Like forAll , but without printing the generated value.

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

Like forAllShrink , but without printing the generated value.

shrinking Source #

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 Source #

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 Source #

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

discard :: a Source #

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 Source #

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

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

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

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

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

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

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.

Note: if your property does no quantification, it will only be tested once. To test it repeatedly, use again .

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

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 Source #

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 Source #

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 Source #

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

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

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 Source #

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)

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

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

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

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

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

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 Source #

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 Source #

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

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

Take the conjunction of several properties.

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

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

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

Take the disjunction of several properties.

What to do on failure

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

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

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

Deprecated: Use counterexample instead

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

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

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

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

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 Source #

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 Source #

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 Source #

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 Source #

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 Source #

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 Source #

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 Source #

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, x2 at least p2 percent of the time, 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 Source #

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 Source #

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 Source #

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.

stdConfidence :: Confidence Source #

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 () Source #

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 () Source #

A variant of labelledExamples that takes test arguments.

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

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