HUnit-1.2.2.1: A unit testing framework for HaskellContentsIndex
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
(~=?) :: (Eq a, Show a) => a -> a -> Test
(~?=) :: (Eq a, Show a) => a -> a -> Test
(~:) :: Testable t => String -> t -> Test
(~?) :: AssertionPredicable t => t -> String -> Test
assertFailure :: String -> Assertion
assertBool :: String -> Bool -> Assertion
assertEqual :: (Eq a, Show a) => String -> a -> a -> Assertion
assertString :: String -> Assertion
type Assertion = IO ()
(@=?) :: (Eq a, Show a) => a -> a -> Assertion
(@?=) :: (Eq a, Show a) => a -> a -> Assertion
(@?) :: AssertionPredicable t => t -> String -> Assertion
class Assertable t where
assert :: t -> Assertion
class ListAssertable t where
listAssert :: [t] -> Assertion
type AssertionPredicate = IO Bool
class AssertionPredicable t where
assertionPredicate :: t -> AssertionPredicate
class Testable t where
test :: t -> Test
data State = State {
path :: Path
counts :: Counts
}
data Counts = Counts {
cases :: Int
tried :: Int
errors :: Int
failures :: Int
}
type Path = [Node]
data Node
= ListItem Int
| Label String
testCasePaths :: Test -> [Path]
testCaseCount :: Test -> Int
type ReportStart us = State -> us -> IO us
type ReportProblem us = 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 AssertionA single, independent test case composed.
TestList [Test]A set of Tests sharing the same level in the hierarchy.
TestLabel String TestA name or description for a subtree of the Tests.
show/hide Instances
(~=?)
:: (Eq a, Show a)
=> aThe actual value
-> a
-> 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).
(~?=)
:: (Eq a, Show a)
=> aThe expected value
-> a
-> 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).
(~:) :: Testable t => String -> t -> Test

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.

(~?)
:: AssertionPredicable t
=> tA message that is displayed on test failure
-> String
-> Test
Creates a test case resulting from asserting the condition obtained from the specified AssertionPredicable.
Making assertions
assertFailure
:: StringA 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
:: StringThe message that is displayed if the assertion fails
-> BoolThe condition
-> Assertion
Asserts that the specified condition holds.
assertEqual
:: (Eq a, Show a)
=> StringThe expected value
-> aThe actual value
-> a
-> 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
:: StringThe 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.

(@=?)
:: (Eq a, Show a)
=> aThe actual value
-> a
-> Assertion
Asserts that the specified actual value is equal to the expected value (with the expected value on the left-hand side).
(@?=)
:: (Eq a, Show a)
=> aThe expected value
-> a
-> Assertion
Asserts that the specified actual value is equal to the expected value (with the actual value on the left-hand side).
(@?)
:: AssertionPredicable t
=> tA message that is displayed if the assertion fails
-> String
-> 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 Assertions 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, Tests and Testable should be used.

Methods
assert :: t -> Assertion
show/hide Instances
class ListAssertable t where
A specialized form of Assertable to handle lists.
Methods
listAssert :: [t] -> Assertion
show/hide Instances
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
show/hide Instances
class Testable t where
Provides a way to convert data into a Test or set of Test.
Methods
test :: t -> Test
show/hide Instances
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
path :: Path
counts :: Counts
show/hide Instances
data Counts
A data structure that hold the results of tests that have been performed up until this point.
Constructors
Counts
cases :: Int
tried :: Int
errors :: Int
failures :: Int
show/hide Instances
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 Paths.
Constructors
ListItem Int
Label String
show/hide Instances
testCasePaths :: Test -> [Path]
Determines the paths for all TestCases in a tree of Tests.
testCaseCount :: Test -> Int
Counts the number of TestCases in a tree of Tests.
type ReportStart us = State -> us -> IO us
Report generator for reporting the start of a test run.
type ReportProblem us = 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
::
=> ReportStart usreport generator for errors during the test run
-> ReportProblem usreport generator for assertion failures during the test run
-> ReportProblem us
-> usthe test to be executed
-> Test
-> 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.

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