# Test.QuickCheck

- Package
- purescript-quickcheck
- Repository
- purescript/purescript-quickcheck

This module is a partial port of the Haskell QuickCheck library.

QuickCheck provides a way to write *property-based* tests.

The `Arbitrary`

and `CoArbitrary`

type classes allow us to create
random data with which we can run our tests. This module provides
instances of both classes for PureScript's core data structures,
as well as functions for writing new instances.

Test suites can use the `quickCheck`

and `quickCheckPure`

functions
to test properties.

For example:

```
main = quickCheck \n -> n + 1 > n
```

### #quickCheck Source

`quickCheck :: forall prop. Testable prop => prop -> Effect Unit`

Test a property.

This function generates a new random seed, runs 100 tests and prints the test results to the console.

### #quickCheckGen Source

`quickCheckGen :: forall prop. Testable prop => Gen prop -> Effect Unit`

A version of `quickCheck`

with the property specialized to `Gen`

.

The `quickCheckGen`

variants are useful for writing property tests where a
`MonadGen`

constraint (or QuickCheck's `Gen`

directly) is being used,
rather than relying on `Arbitrary`

instances. Especially useful for the
`MonadGen`

-constrained properties as they will not infer correctly when
used with the `quickCheck`

functions unless an explicit type annotation is
used.

### #quickCheck' Source

`quickCheck' :: forall prop. Testable prop => Int -> prop -> Effect Unit`

A variant of the `quickCheck`

function which accepts an extra parameter
representing the number of tests which should be run.

### #quickCheckPure' Source

`quickCheckPure' :: forall prop. Testable prop => Seed -> Int -> prop -> List (Tuple Seed Result)`

Test a property, returning all test results as a List, with the Seed that was used for each result.

The first argument is the *random seed* to be passed to the random generator.
The second argument is the number of tests to run.

### #checkResults Source

`checkResults :: List (Tuple Seed Result) -> ResultSummary`

Processes the results from `quickCheckPure'`

to produce a `ResultSummary`

.

### #printSummary Source

`printSummary :: ResultSummary -> String`

Print a one-line summary in the form "x/y test(s) passed."

### #Testable Source

`class Testable prop where`

The `Testable`

class represents *testable properties*.

A testable property is a function of zero or more `Arbitrary`

arguments,
returning a `Boolean`

or `Result`

.

Testable properties can be passed to the `quickCheck`

function.

#### Members

#### Instances

### #assertEquals Source

`assertEquals :: forall a. Eq a => Show a => a -> a -> Result`

Self-documenting equality assertion

### #assertNotEquals Source

`assertNotEquals :: forall a. Eq a => Show a => a -> a -> Result`

Self-documenting inequality assertion

### #(>=?) Source

Operator alias for Test.QuickCheck.assertGreaterThanEq *(non-associative / precedence 2)*

## Re-exports from **Random.**LCG

### #randomSeed Source

`randomSeed :: Effect Seed`

Create a random seed

## Re-exports from **Test.**QuickCheck.Arbitrary

### #Arbitrary Source

`class Arbitrary t where`

The `Arbitrary`

class represents those types whose values can be
*randomly-generated*.

`arbitrary`

uses the `Gen`

monad to express a random generator for
the type `t`

. Combinators in the `Test.QuickCheck.Gen`

module can be used to construct random generators.

#### Members

#### Instances

`Arbitrary Boolean`

`Arbitrary Number`

`Arbitrary Int`

`Arbitrary String`

`Arbitrary NonEmptyString`

`Arbitrary Char`

`Arbitrary Unit`

`Arbitrary Ordering`

`(Arbitrary a) => Arbitrary (Array a)`

`(Arbitrary a) => Arbitrary (NonEmptyArray a)`

`(Coarbitrary a, Arbitrary b) => Arbitrary (a -> b)`

`(Arbitrary a, Arbitrary b) => Arbitrary (Tuple a b)`

`(Arbitrary a) => Arbitrary (Maybe a)`

`(Arbitrary a, Arbitrary b) => Arbitrary (Either a b)`

`(Arbitrary a) => Arbitrary (List a)`

`(Arbitrary a) => Arbitrary (Identity a)`

`(Arbitrary a) => Arbitrary (Lazy a)`

`(Arbitrary (f a), Arbitrary a) => Arbitrary (NonEmpty f a)`

`(Arbitrary a) => Arbitrary (NonEmptyList a)`

`Arbitrary NoArguments`

`(Arbitrary l, ArbitraryGenericSum r) => Arbitrary (Sum l r)`

`(Arbitrary l, Arbitrary r) => Arbitrary (Product l r)`

`(Arbitrary a) => Arbitrary (Constructor s a)`

`(Arbitrary a) => Arbitrary (Argument a)`

`(RowToList row list, ArbitraryRowList list row) => Arbitrary (Record row)`

### #Coarbitrary Source

`class Coarbitrary t where`

The `Coarbitrary`

class represents types which appear on the left of
an `Arbitrary`

function arrow.

To construct an `Arbitrary`

instance for the type `a -> b`

, we need to
use the input of type `a`

to *perturb* a random generator for `b`

. This
is the role of the `coarbitrary`

function.

`Coarbitrary`

instances can be written using the `perturbGen`

function.

#### Members

`coarbitrary :: forall r. t -> Gen r -> Gen r`

#### Instances

`Coarbitrary Boolean`

`Coarbitrary Number`

`Coarbitrary Int`

`Coarbitrary String`

`Coarbitrary NonEmptyString`

`Coarbitrary Char`

`Coarbitrary Unit`

`Coarbitrary Ordering`

`(Coarbitrary a) => Coarbitrary (Array a)`

`(Coarbitrary a) => Coarbitrary (NonEmptyArray a)`

`(Arbitrary a, Coarbitrary b) => Coarbitrary (a -> b)`

`(Coarbitrary a, Coarbitrary b) => Coarbitrary (Tuple a b)`

`(Coarbitrary a) => Coarbitrary (Maybe a)`

`(Coarbitrary a, Coarbitrary b) => Coarbitrary (Either a b)`

`(Coarbitrary a) => Coarbitrary (List a)`

`(Coarbitrary a) => Coarbitrary (Identity a)`

`(Coarbitrary a) => Coarbitrary (Lazy a)`

`(Coarbitrary (f a), Coarbitrary a) => Coarbitrary (NonEmpty f a)`

`(Coarbitrary a) => Coarbitrary (NonEmptyList a)`

`Coarbitrary NoArguments`

`(Coarbitrary l, Coarbitrary r) => Coarbitrary (Sum l r)`

`(Coarbitrary l, Coarbitrary r) => Coarbitrary (Product l r)`

`(Coarbitrary a) => Coarbitrary (Constructor s a)`

`(Coarbitrary a) => Coarbitrary (Argument a)`