7.8: The Implementation of SUnit
- Page ID
- 38019
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)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