Test.Tasty

This module defines the main data types and functions needed to use Tasty.

To create a test suite, you also need one or more test providers, such as tasty-hunit or tasty-quickcheck.

A simple example (using tasty-hunit) is

import Test.Tasty
import Test.Tasty.HUnit

main = defaultMain tests

tests :: TestTree
tests = testGroup "Tests"
  [ testCase "2+2=4" $
      2+2 @?= 4
  , testCase "7 is even" $
      assertBool "Oops, 7 is odd" (even 7)
  ]

Take a look at the README: it contains a comprehensive list of test providers, a bigger example, and a lot of other information.

Organizing tests

type TestName = String

The name of a test or a group of tests

data TestTree

The main data structure defining a test suite.

It consists of individual test cases and properties, organized in named groups which form a tree-like hierarchy.

There is no generic way to create a test case. Instead, every test provider (tasty-hunit, tasty-smallcheck etc.) provides a function to turn a test case into a TestTree.

Groups can be created using testGroup.

testGroup :: TestName -> [TestTree] -> TestTree

Create a named group of test cases or other groups

Running tests

defaultMain :: TestTree -> IO ()

Parse the command line arguments and run the tests.

When the tests finish, this function calls exitWith with the exit code that indicates whether any tests have failed. Most external systems (stack, cabal, travis-ci, jenkins etc.) rely on the exit code to detect whether the tests pass. If you want to do something else after defaultMain returns, you need to catch the exception and then re-throw it. Example:

import Test.Tasty
import Test.Tasty.HUnit
import System.Exit
import Control.Exception

test = testCase "Test 1" (2 @?= 3)

main = defaultMain test
  `catch` (\e -> do
    if e == ExitSuccess
      then putStrLn "Yea"
      else putStrLn "Nay"
    throwIO e)

defaultMainWithIngredients :: [Ingredient] -> TestTree -> IO ()

Parse the command line arguments and run the tests using the provided ingredient list.

When the tests finish, this function calls exitWith with the exit code that indicates whether any tests have failed. See defaultMain for details.

defaultIngredients :: [Ingredient]

List of the default ingredients. This is what defaultMain uses.

At the moment it consists of listingTests and consoleTestReporter.

includingOptions :: [OptionDescription] -> Ingredient

This ingredient doesn't do anything apart from registering additional options.

The option values can be accessed using askOption.

Adjusting and querying options

Normally options are specified on the command line. But you can also have different options for different subtrees in the same tree, using the functions below.

Note that ingredient options (number of threads, hide successes etc.) set in this way will not have any effect. This is for modifying per-test options, such as timeout, number of generated tests etc.

adjustOption :: IsOption v => (v -> v) -> TestTree -> TestTree

Locally adjust the option value for the given test subtree

localOption :: IsOption v => v -> TestTree -> TestTree

Locally set the option value for the given test subtree

askOption :: IsOption v => (v -> TestTree) -> TestTree

Customize the test tree based on the run-time options

Standard options

data Timeout

Timeout to be applied to individual tests

Constructors

Timeout Integer String

String is the original representation of the timeout (such as "0.5m"), so that we can print it back. Integer is the number of microseconds.

NoTimeout

Instances

Show Timeout

Methods

showsPrec :: Int -> Timeout -> ShowS

show :: Timeout -> String

showList :: [Timeout] -> ShowS

IsOption Timeout

Methods

defaultValue :: Timeout

parseValue :: String -> Maybe Timeout

optionName :: Tagged * Timeout String

optionHelp :: Tagged * Timeout String

optionCLParser :: Parser Timeout

mkTimeout

Arguments

:: Integer

microseconds

-> Timeout

A shortcut for creating Timeout values

Resources

Sometimes several tests need to access the same resource — say, a file or a socket. We want to create or grab the resource before the tests are run, and destroy or release afterwards.

withResource

Arguments

:: IO a

initialize the resource

-> (a -> IO ())

free the resource

-> (IO a -> TestTree)

IO a is an action which returns the acquired resource. Despite it being an IO action, the resource it returns will be acquired only once and shared across all the tests in the tree.

-> TestTree

Acquire the resource to run this test (sub)tree and release it afterwards