quickCheck is:module

The QuickCheck manual gives detailed information about using QuickCheck effectively. You can also try https://begriffs.com/posts/2017-01-14-design-use-quickcheck.html, a tutorial written by a user of QuickCheck. To start using QuickCheck, write down your property as a function returning Bool. For example, to check that reversing a list twice gives back the same list you can write:

import Test.QuickCheck

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

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

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

To run more tests you can use the withMaxSuccess combinator:

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

To use QuickCheck on your own data types you will need to write Arbitrary instances for those types. See the QuickCheck manual for details about how to do that. When testing fails quickCheck will try to give you a minimal counterexample to your property: @ import Test.QuickCheck prop_reverse_bad :: [Int] -> Bool prop_reverse_bad xs = reverse xs == xs

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

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

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

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

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

This module allows to use QuickCheck properties in tasty.

Provides Arbitrary instances for protocol types.

QuickCheck related utilities.

QuickCheck integration for Predicate

Use QuickCheck generators and Arbitrary instances with Hedgehog.

Servant.QuickCheck provides utilities related to using QuickCheck over an API. Rather than specifying properties that individual handlers must satisfy, you can state properties that ought to hold true of the entire API. While the API must be described with servant types, the server being tested itself need not be implemented with servant-server (or indeed, written in Haskell). The documentation of the Useful predicates sections is meant to serve as a set of helpful pointers for learning more about best practices concerning REST APIs.

Functions for introducing QuickCheck tests into a Sandwich test tree. Modelled after Hspec's version. Documentation can be found here.

Allows QuickCheck2 properties to be used with the test-framework package. For an example of how to use test-framework, please see https://github.com/haskell/test-framework/raw/master/example/Test/Framework/Example.lhs.

This module integrates the QuickCheck library into HTF. It re-exports all functionality of QuickCheck and defines some additional functions.