Test a Little, Code a Little Colin Sharples IBM Global Services New Zealand Colin Sharples IBM Global Services New Zealand

Overview JUnit –a Java instance of the Gamma/Beck xUnit framework architecture Automates unit testing Promotes a development philosophy of: “Test a Little, Code a Little”

Talk outline Why do unit testing? Framework description Development Philosophy Extensions Demo

Why do unit testing?

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Framework description

What is a unit test? Exercises a “unit” of production code –in isolation from rest of system –checks results are as expected A “unit” is a coherent piece of functionality –Java class or package

TestCase Encapsulates the set of tests for one unit –public void testXxx() {} Contains the “fixture” for multiple tests –public void setUp() {} –public void tearDown() {} Implements the Command pattern –public void run(TestResult result) {}

Assert Methods for checking test conditions –assertTrue() –assertNull() –assertNotNull() –assertEquals() –assertSame –fail()

TestSuite Collects tests and test cases into suites –a suite for all the tests in a single test case –a suite for all the test cases in a package –a suite for all test cases in a component –a suite for all test cases in an application

TestResult Gathers results from tests –failures (anticipated, check by assertions) –errors (unanticipated, e.g. runtime exceptions) Collates all results from a single suite Can check if an error should stop the test run

TestRunner Provides a runtime execution environment Runs individual tests or suites Graphical and text based user interfaces –Swing interface –Text interface integrates with Ant –Plugin for Eclipse

Extension Points Extend TestCase or TestSuite –ExceptionTestCase –ActiveTestSuite Provide additional testing support –TestDecorator –TestSetup Your extension here...

Development Philosophy

Test a little, code a little Core philosophy –write tests first –then write the code to make the tests work –when the tests work, you’re done :-)

Unit testing saves time Unit tests exercise the design Unit tests give the developer confidence Unit tests speed up integration testing

Automation is the key Tests are useless if they are not run JUnit allows easy automation of tests Automatic tests ease integration testing Automatic tests ease regression testing Automatic tests allow installation verification

Test case organisation Two options: –place test cases in a “test” sub-directory –place test cases in same package in a different source tree Allow for separation of test code and production code

JUnit Extensions

Example JUnit extensions StrutsTestCase –automated testing of Jakarta Struts applications JXUnit –provides support for data centric testing HttpUnit –automated web site testing

Resources –articles, hints & tips –downloads –Eclipse IDE –junit plugin