Test.HUnit.Base

HUnit-1.3.1.1: A unit testing framework for Haskell

Safe Haskell | Safe
Language | Haskell98

Test.HUnit.Base

Contents

- Declaring tests
- Making assertions
- Extending the assertion functionality
- Test execution

Description

Basic definitions for the HUnit library.

This module contains what you need to create assertions and test cases and combine them into test suites.

This module also provides infrastructure for implementing test controllers (which are used to execute tests). See Test.HUnit.Text for a great example of how to implement a test controller.

Synopsis

- data Test
  - = TestCase Assertion
  - | TestList [Test]
  - | TestLabel String Test
- (~=?) :: (?loc :: CallStack) => (Eq a, Show a) => a -> a -> Test
- (~?=) :: (?loc :: CallStack) => (Eq a, Show a) => a -> a -> Test
- (~:) :: (?loc :: CallStack) => Testable t => String -> t -> Test
- (~?) :: (?loc :: CallStack) => AssertionPredicable t => t -> String -> Test
- assertFailure :: (?loc :: CallStack) => String -> Assertion
- assertBool :: (?loc :: CallStack) => String -> Bool -> Assertion
- assertEqual :: (?loc :: CallStack) => (Eq a, Show a) => String -> a -> a -> Assertion
- assertString :: (?loc :: CallStack) => String -> Assertion
- type Assertion = IO ()
- (@=?) :: (?loc :: CallStack) => (Eq a, Show a) => a -> a -> Assertion
- (@?=) :: (?loc :: CallStack) => (Eq a, Show a) => a -> a -> Assertion
- (@?) :: (?loc :: CallStack) => AssertionPredicable t => t -> String -> Assertion
- class Assertable t where
  - assert :: (?loc :: CallStack) => t -> Assertion
- class ListAssertable t where
  - listAssert :: (?loc :: CallStack) => [t] -> Assertion
- type AssertionPredicate = IO Bool
- class AssertionPredicable t where
  - assertionPredicate :: t -> AssertionPredicate
- class Testable t where
  - test :: (?loc :: CallStack) => t -> Test
- data State = State {
  - path :: Path
  - counts :: Counts
  }
- data Counts = Counts {
  - cases, tried, errors, failures :: Int
  }
- type Path = [Node]
- data Node
  - = ListItem Int
  - | Label String
- testCasePaths :: Test -> [Path]
- testCaseCount :: Test -> Int
- data Location = Location {
  - locationFile :: FilePath
  - locationLine :: Int
  - locationColumn :: Int
  }
- type ReportStart us = State -> us -> IO us
- type ReportProblem us = Maybe Location -> String -> State -> us -> IO us
- performTest :: ReportStart us -> ReportProblem us -> ReportProblem us -> us -> Test -> IO (Counts, us)

## Declaring tests

data Test

The basic structure used to create an annotated tree of test cases.

Constructors

TestCase Assertion | A single, independent test case composed.
TestList [Test] | A set of `Test`s sharing the same level in the hierarchy.
TestLabel String Test | A name or description for a subtree of the `Test`s.

Instances

Show Test |
Testable Test |

(~=?) infix 1

Arguments

:: (?loc :: CallStack) |
=> (Eq a, Show a) |
=> a | The expected value
-> a | The actual value
-> Test |

Shorthand for a test case that asserts equality (with the expected value on the left-hand side, and the actual value on the right-hand side).

(~?=) infix 1

Arguments

:: (?loc :: CallStack) |
=> (Eq a, Show a) |
=> a | The actual value
-> a | The expected value
-> Test |

Shorthand for a test case that asserts equality (with the actual value on the left-hand side, and the expected value on the right-hand side).

(~:) :: (?loc :: CallStack) => Testable t => String -> t -> Test infixr 0

Creates a test from the specified `Testable`, with the specified label attached to it.

Since `Test` is `Testable`, this can be used as a shorthand way of attaching a `TestLabel` to one or more tests.

(~?) infix 1

Arguments

:: (?loc :: CallStack) |
=> AssertionPredicable t |
=> t | A value of which the asserted condition is predicated
-> String | A message that is displayed on test failure
-> Test |

Creates a test case resulting from asserting the condition obtained from the specified `AssertionPredicable`.

## Making assertions

assertFailure

Arguments

:: (?loc :: CallStack) |
=> String | A message that is displayed with the assertion failure
-> Assertion |

Unconditionally signals that a failure has occured. All other assertions can be expressed with the form:

       if conditionIsMet
           then IO ()
           else assertFailure msg

assertBool

Arguments

:: (?loc :: CallStack) |
=> String | The message that is displayed if the assertion fails
-> Bool | The condition
-> Assertion |

Asserts that the specified condition holds.

assertEqual

Arguments

:: (?loc :: CallStack) |
=> (Eq a, Show a) |
=> String | The message prefix
-> a | The expected value
-> a | The actual value
-> Assertion |

Asserts that the specified actual value is equal to the expected value. The output message will contain the prefix, the expected value, and the actual value.

If the prefix is the empty string (i.e., `""`), then the prefix is omitted and only the expected and actual values are output.

assertString

Arguments

:: (?loc :: CallStack) |
=> String | The message that is displayed with the assertion failure
-> Assertion |

Signals an assertion failure if a non-empty message (i.e., a message other than `""`) is passed.

type Assertion = IO ()

When an assertion is evaluated, it will output a message if and only if the assertion fails.

Test cases are composed of a sequence of one or more assertions.

(@=?) infix 1

Arguments

:: (?loc :: CallStack) |
=> (Eq a, Show a) |
=> a | The expected value
-> a | The actual value
-> Assertion |

Asserts that the specified actual value is equal to the expected value (with the expected value on the left-hand side).

(@?=) infix 1

Arguments

:: (?loc :: CallStack) |
=> (Eq a, Show a) |
=> a | The actual value
-> a | The expected value
-> Assertion |

Asserts that the specified actual value is equal to the expected value (with the actual value on the left-hand side).

(@?) infix 1

Arguments

:: (?loc :: CallStack) |
=> AssertionPredicable t |
=> t | A value of which the asserted condition is predicated
-> String | A message that is displayed if the assertion fails
-> Assertion |

Asserts that the condition obtained from the specified `AssertionPredicable` holds.

## Extending the assertion functionality

class Assertable t where

Allows the extension of the assertion mechanism.

Since an `Assertion` can be a sequence of `Assertion`s and `IO` actions, there is a fair amount of flexibility of what can be achieved. As a rule, the resulting `Assertion` should be the body of a `TestCase` or part of a `TestCase`; it should not be used to assert multiple, independent conditions.

If more complex arrangements of assertions are needed, `Test`s and `Testable` should be used.

Methods

assert :: (?loc :: CallStack) => t -> Assertion

Instances

Assertable Bool |
Assertable () |
ListAssertable t => Assertable [t] |
Assertable t => Assertable (IO t) |

class ListAssertable t where

A specialized form of `Assertable` to handle lists.

Methods

listAssert :: (?loc :: CallStack) => [t] -> Assertion

Instances

ListAssertable Char |

type AssertionPredicate = IO Bool

The result of an assertion that hasn't been evaluated yet.

Most test cases follow the following steps:

1. Do some processing or an action.
2. Assert certain conditions.

However, this flow is not always suitable. `AssertionPredicate` allows for additional steps to be inserted without the initial action to be affected by side effects. Additionally, clean-up can be done before the test case has a chance to end. A potential work flow is:

1. Write data to a file.
2. Read data from a file, evaluate conditions.
3. Clean up the file.
4. Assert that the side effects of the read operation meet certain conditions.
5. Assert that the conditions evaluated in step 2 are met.

class AssertionPredicable t where

Used to signify that a data type can be converted to an assertion predicate.

Methods

assertionPredicate :: t -> AssertionPredicate

Instances

AssertionPredicable Bool |
AssertionPredicable t => AssertionPredicable (IO t) |

class Testable t where

Provides a way to convert data into a `Test` or set of `Test`.

Methods

test :: (?loc :: CallStack) => t -> Test

Instances

Testable Test |
Testable t => Testable [t] |
Assertable t => Testable (IO t) |

## Test execution

Note: the rest of the functionality in this module is intended for implementors of test controllers. If you just want to run your tests cases, simply use a test controller, such as the text-based controller in Test.HUnit.Text.

data State

Keeps track of the remaining tests and the results of the performed tests. As each test is performed, the path is removed and the counts are updated as appropriate.

Constructors

State |
Fields path :: Path counts :: Counts

Instances

Eq State |
Read State |
Show State |

data Counts

A data structure that hold the results of tests that have been performed up until this point.

Constructors

Counts |
Fields cases, tried, errors, failures :: Int

Instances

Eq Counts |
Read Counts |
Show Counts |

type Path = [Node]

Uniquely describes the location of a test within a test hierarchy. Node order is from test case to root.

data Node

Composed into `Path`s.

Constructors

ListItem Int |
Label String |

Instances

Eq Node |
Read Node |
Show Node |

testCasePaths :: Test -> [Path]

Determines the paths for all `TestCase`s in a tree of `Test`s.

testCaseCount :: Test -> Int

Counts the number of `TestCase`s in a tree of `Test`s.

data Location

Constructors

Location |
Fields locationFile :: FilePath locationLine :: Int locationColumn :: Int

Instances

Eq Location |
Ord Location |
Show Location |

type ReportStart us = State -> us -> IO us

Report generator for reporting the start of a test run.

type ReportProblem us = Maybe Location -> String -> State -> us -> IO us

Report generator for reporting problems that have occurred during a test run. Problems may be errors or assertion failures.

performTest

Arguments

:: ReportStart us | report generator for the test run start
-> ReportProblem us | report generator for errors during the test run
-> ReportProblem us | report generator for assertion failures during the test run
-> us |
-> Test | the test to be executed
-> IO (Counts, us) |

Performs a test run with the specified report generators.

This handles the actual running of the tests. Most developers will want to use `HUnit.Text.runTestTT` instead. A developer could use this function to execute tests via another IO system, such as a GUI, or to output the results in a different manner (e.g., upload XML-formatted results to a webservice).

Note that the counts in a start report do not include the test case being started, whereas the counts in a problem report do include the test case just finished. The principle is that the counts are sampled only between test case executions. As a result, the number of test case successes always equals the difference of test cases tried and the sum of test case errors and failures.