Test.QuickCheck.Property

Combinators for constructing properties.

Property and Testable types

newtype Property

The type of properties.

Constructors

MkProperty

Fields

unProperty :: Gen Prop

Instances

Testable Property

class Testable prop where

The class of things which can be tested, i.e. turned into a property.

Methods

property :: prop -> Property

Convert the thing to a property.

exhaustive :: prop -> Bool

If true, the property will only be tested once. However, if used inside a quantifier, it will be tested normally.

Instances

Testable Bool

Testable Result

Testable Prop

Testable Discard

Testable Property

Testable prop => Testable (Gen prop)

(Arbitrary a, Show a, Testable prop) => Testable (a -> prop)

data Discard

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

Constructors

Discard

Instances

Testable Discard

morallyDubiousIOProperty :: Testable prop => IO prop -> Property

Deprecated: Use ioProperty instead

Do I/O inside a property. This can obviously lead to unrepeatable testcases, so use with care.

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

Do I/O inside a property. This can obviously lead to unrepeatable testcases, so use with care.

For more advanced monadic testing you may want to look at Test.QuickCheck.Monadic.

Exception handling

protect :: (AnException -> a) -> IO a -> IO a

Type Prop

newtype Prop

Constructors

MkProp

Fields

unProp :: Rose Result

Instances

Testable Prop

type Rose

data Rose a

Constructors

MkRose a [Rose a]

IORose (IO (Rose a))

Instances

Monad Rose

Functor Rose

Applicative Rose

ioRose :: IO (Rose Result) -> Rose Result

joinRose :: Rose (Rose a) -> Rose a

reduceRose :: Rose Result -> IO (Rose Result)

onRose :: (a -> [Rose a] -> Rose a) -> Rose a -> Rose a

protectRose :: IO (Rose Result) -> IO (Rose Result)

protectResults :: Rose Result -> Rose Result

Result type

data Callback

Different kinds of callbacks

Constructors

PostTest CallbackKind (State -> Result -> IO ())

Called just after a test

PostFinalFailure CallbackKind (State -> Result -> IO ())

Called with the final failing test-case

data CallbackKind

Constructors

Counterexample

Affected by the verbose combinator

NotCounterexample

Not affected by the verbose combinator

data Result

The result of a single test.

Constructors

MkResult

Fields

ok :: Maybe Bool

result of the test case; Nothing = discard

expect :: Bool

indicates what the expected result of the property is

reason :: String

a message indicating what went wrong

theException :: Maybe AnException

the exception thrown, if any

abort :: Bool

if True, the test should not be repeated

stamp :: [(String, Int)]

the collected values for this test case

callbacks :: [Callback]

the callbacks for this test case

Instances

Testable Result

result :: Result

exception :: String -> AnException -> Result

formatException :: String -> AnException -> String

protectResult :: IO Result -> IO Result

succeeded :: Result

failed :: Result

rejected :: Result

Lifting and mapping functions

liftBool :: Bool -> Result

mapResult :: Testable prop => (Result -> Result) -> prop -> Property

mapTotalResult :: Testable prop => (Result -> Result) -> prop -> Property

mapRoseResult :: Testable prop => (Rose Result -> Rose Result) -> prop -> Property

mapProp :: Testable prop => (Prop -> Prop) -> prop -> Property

Property combinators

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

Changes the maximum test case size for a property.

shrinking

Arguments

:: Testable prop

=> (a -> [a])

shrink-like function.

-> a

The original argument

-> (a -> prop)

-> Property

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

noShrinking :: Testable prop => prop -> Property

Disables shrinking for a property altogether.

callback :: Testable prop => Callback -> prop -> Property

Adds a callback

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

Adds the given string to the counterexample.

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

Deprecated: Use counterexample instead

Adds the given string to the counterexample.

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.

verbose :: Testable prop => prop -> Property

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

expectFailure :: Testable prop => prop -> Property

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

once :: Testable prop => prop -> Property

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

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

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

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

Labels a property with a value:

 collect x = label (show x)

classify

Arguments

:: Testable prop

=> Bool

True if the test case should be labelled.

-> String

Label.

-> prop

-> Property

Conditionally labels test case.

cover

Arguments

:: Testable prop

=> Bool

True if the test case belongs to the class.

-> Int

The required percentage (0-100) of test cases.

-> String

Label for the test case class.

-> prop

-> Property

Checks that at least the given proportion of the test cases belong to the given class.

(==>) :: Testable prop => Bool -> prop -> Property

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.

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

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

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.

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

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

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

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

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

Take the disjunction of several properties.

(===) :: (Eq a, Show a) => a -> a -> Property

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