Safe Haskell	Safe
Language	Haskell98

Test.QuickCheck.Property

Contents

Property and Testable types

Description

Combinators for constructing properties.

Synopsis

Property and Testable types

newtype Property Source

The type of properties.

Backwards combatibility note: in older versions of QuickCheck Property was a type synonym for Gen Prop, so you could mix and match property combinators and Gen monad operations. Code that does this will no longer typecheck. However, it is easy to fix: because of the Testable typeclass, any combinator that expects a Property will also accept a Gen Property. If you have a Property where you need a Gen a, simply wrap the property combinator inside a return to get a Gen Property, and all should be well.

Constructors

MkProperty
Fields unProperty :: Gen Prop

Instances

Testable Property

class Testable prop where Source

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

Minimal complete definition

property

Methods

property :: prop -> Property Source

Convert the thing to a property.

exhaustive :: prop -> Bool Source

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 Source

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 Source

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 Source

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 Source

Type Prop

newtype Prop Source

Constructors

MkProp
Fields unProp :: Rose Result

Instances

Testable Prop

type Rose

data Rose a Source

Constructors

MkRose a [Rose a]
IORose (IO (Rose a))

Instances

Monad Rose
Functor Rose
Applicative Rose

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

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

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

Execute the IORose bits of a rose tree, returning a tree constructed by MkRose.

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

Apply a function to the outermost MkRose constructor of a rose tree. The function must be total!

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

Wrap a rose tree in an exception handler.

protectResults :: Rose Result -> Rose Result Source

Wrap all the Results in a rose tree in exception handlers.

Result type

data Callback Source

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 Source

Constructors

Counterexample	Affected by the `verbose` combinator
NotCounterexample	Not affected by the `verbose` combinator

data Result Source

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
labels :: Map String Int: all labels used by this property
stamp :: Set String: the collected values for this test case
callbacks :: [Callback]: the callbacks for this test case

Instances

Testable Result

exception :: String -> AnException -> Result Source

formatException :: String -> AnException -> String Source

protectResult :: IO Result -> IO Result Source

succeeded :: Result Source

rejected :: Result Source

failed :: Result Source

Lifting and mapping functions

liftBool :: Bool -> Result Source

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

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

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

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

Property combinators

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

Changes the maximum test case size for a property.

shrinking Source

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 Source

Disables shrinking for a property altogether.

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

Adds a callback

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

Adds the given string to the counterexample.

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

Deprecated: Use counterexample instead

Adds the given string to the counterexample.

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.

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

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 Source

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

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

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

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

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

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

Labels a property with a value:

collect x = label (show x)

classify Source

Arguments

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

Conditionally labels test case.

cover Source

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

(==>) :: 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.

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

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 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.

(.&.) :: (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.

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

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