Unit testing Java programs Using JUnit

1. Unit testing Java programsUsing JUnit “If it isn't tested, it doesn’t work” Unit testing Java programs

2. Requirements for tests • Tests must be executable • A test must clearly show whether it executed successfully or not • The not-so-successful part of the test must not be buried in a pile of test reports. Unit testing Java programs

3. Which methods should be tested • Test a method if you are not 100% sure that the method is correct. • Methods that usually does not need testing • Simple get and set methods • However, you might call get and set methods in testing other (more complex) methods • Simple toString methods Unit testing Java programs

4. Individual test cases • Annotate the test method with @org.junit.Test • No need to extends any classes or use special method names • Unlike JUnit 3 • Generally you would like one test class pr. Java class • The unit to test is a class. Unit testing Java programs

5. Fixtures: Before and After • Sometimes you have 2 or more tests that must run on the same data. • To ease this JUnit introduces the concept of a “fixture”. • You can annotate 2 methods in your test class from • @org.junit.Before • Executed before each individual test • Used to initialize test data • Used quite often • @org.junit.After • Executed after each individual test • Used to clean up after the test • Examples: Close database or socket connections • Not used very often Unit testing Java programs

6. How to test exceptions • JUnit 3: Testing an expected exception try { method(); fail(“Exception expected”); } catch (ExpectedException ex) { /* ignore */ } • JUnit 4: Testing an expected exception • Use an annotation • @Test (expected = SomeException.class) public void testMetod() { … } • If testMethod() does not throw SomeException the test fails. Unit testing Java programs

7. NetBeans assistance • JUnit is a plugin to NetBeans • And many other IDE’s • NetBeans can assist you in making TestCases for individual Java class and in assembling the test cases into test suites. • Right click the class you want to test • Tools →JUnit tests • Choose JUnit 4 (not JUnit 3) • JUnit generates empty tests for each public / protected method in a Java class. • Fill you the empty tests and run the test. • Like you run an ordinary program Unit testing Java programs

8. Testing in XP • Testing is an important discipline in XP (Extreme Programming) • XP idea: Create the test before the code to be tested • Writing the test makes you thing about detailed design • Test is an executable requirements • Writing (and running) test will be a positive experience. • We know when a class is done • When all tests run Unit testing Java programs

9. References Beck & GammaJUnit Cookbook, http://junit.sourceforge.net/doc/cookbook/cookbook.htm Kent Beck & Erich Gamma invented JUnit Kent BeckJUnithttps://github.com/KentBeck/junit/wiki Martin FowlerRefactoring, Addison Wesley 2000 Chapter 4 Building Tests, page 89-102 Extreme Programming, Code the Unit Test Firsthttp://www.extremeprogramming.org/rules/testfirst.html Testing is an important discipline in XP (eXtreme Programming), which is another Kent Bech invention. Alex GarrettJUnit antipatterns http://www-128.ibm.com/developerworks/opensource/library/os-junit Unit testing Java programs