7.8: The Implementation of SUnit

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Andrew P. Black, Stéphane Ducasse, Oscar Nierstrasz, Damien Pollet

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The implementation of SUnit makes an interesting case study of a Smalltalk framework. Let’s look at some key aspects of the implementation by following the execution of a test.

Running one test

To execute one test, we evaluate the expression (aTestClass selector: aSymbol) run.

The method TestCase»run creates an instance of TestResult that will accumulate the results of the tests, then it sends itself the message run:. (See Figure \(\PageIndex{1}\).)

Code \(\PageIndex{1}\) (Squeak): Running a Test Case

TestCase»run
    | result |
    result := TestResult new.
    self run: result.
    ↑result

The method TestCase»run: sends the message runCase: to the test result:

Code \(\PageIndex{2}\) (Squeak): Passing the Test Case to the Test Result

TestCase»run: aResult
    aResult runCase: self

The method TestResult»runCase: sends the message runCase to an individual test, to execute the test. TestResult»runCase deals with any exceptions that may be raised during the execution of a test, runs a TestCase by sending it the message runCase, and counts the errors, failures and passes.

Code \(\PageIndex{3}\) (Squeak): Catching Test Case Errors and Failures

TestResult»runCase: aTestCase
    | testCasePassed |
    testCasePassed := true.
    [[aTestCase runCase]
        on: self class failure
        do:
            [:signal |
            failures add: aTestCase.
            testCasePassed := false.
            signal return: false]]
                on: self class error
                do:
                    [:signal |
                    errors add: aTestCase.
                    testCasePassed := false.
                    signal return: false].
    testCasePassed ifTrue: [passed add: aTestCase]

The method TestCase»runCase sends the messages setUp and tearDown as shown below.

Code \(\PageIndex{4}\) (Squeak): Test Case Template Method

TestCase»runCase
    self setUp.
    [self performTest] ensure: [self tearDown]

Running a TestSuite

To run more than one test, we send the message run to a TestSuite that contains the relevant tests. TestCase class provides some functionality to build a test suite from its methods. The expression MyTestCase buildSuiteFromSelectors returns a suite containing all the tests defined in the MyTestCase class. The core of this process is

Code \(\PageIndex{5}\) (Squeak): Auto-Building the Test Suite

TestCase class»testSelectors
    ↑self selectors asSortedCollection asOrderedCollection select: [:each |
    ('test*' match: each) and: [each numArgs isZero]]

The method TestSuite»run creates an instance of TestResult, verifies that all the resources are available, and then sends itself the message run:, which runs all the tests in the suite. All the resources are then released.

Code \(\PageIndex{6}\) (Squeak): Running a Test Suite

TestSuite»run
    | result |
    result := TestResult new.
    self areAllResourcesAvailable
        ifFalse: [↑TestResult signalErrorWith:
            'Resource could not be initialized'].
    [self run: result] ensure: [self resources do:
        [:each | each reset]].
    ↑result

Code \(\PageIndex{7}\) (Squeak): Passing the Test Suite to the Test Result

TestSuite»run: aResult
    self tests do:
        [:each |
            self sunitChanged: each.
            each run: aResult]

The class TestResource and its subclasses keep track of their currently created instances (one per class) that can be accessed and created using the class method current. This instance is cleared when the tests have finished running and the resources are reset.

The resource availability check makes it possible for the resource to be re-created if needed, as shown in the class method TestResource class»isAvailable. During the TestResource instance creation, it is initialized and the method setUp is invoked.

Code \(\PageIndex{8}\) (Squeak): Test Resource Availability

TestResource class»isAvailable
    ↑self current notNil

Code \(\PageIndex{9}\) (Squeak): Test Resource Creation

TestResource class»current
    current isNil ifTrue: [current := self new].
    ↑current

Code \(\PageIndex{10}\) (Squeak): Test Resource Initialization

TestResource»initialize
    self setUp