JUnit

What is unit testing? A unit is the smallest testable part of an application. A unit test automatically verifies the correctness of the unit. There are other kinds of tests: Stress testing Benchmark testing

Why is testing good? Due to psychological factors, programmers are bad testers. A computer can test much faster than a human “If it ain’t broken, don’t fix it” A change may introduce new bugs => We prefer not to change existing code => Old designs are not updated => The program cannot adapt to new requirements With testing you can easily make aggressive changes Refactoring, XP

Wish list: A testing framework 1. Test expressions: Means for comparing an actual result with an expected result 2. Clear indication of success/failure 3. Clear indication of failed tests 4. Split a long test method into several smaller methods 5. Continue with other tests even if a test fails 6. Continue with other tests even if a test throws an exception 7. No duplication of initialization code of tested objects 8. Side effects should not influence other tests 9. No need to maintain a list of tests

JUnit JUnit: JUnit is a unit testing framework for Java A test case defines tools to run a related collection of tests. A test suite is a collection of test cases, test suites, or both. It is used to aggregate tests that should be executed together.

JUnit: Benefits Writing a test is as simple as writing a method that exercises the code to be tested and defining the expected result. JUnit gives flexibility in grouping tests and convenient ways to capture and/or summarize test failures. The Assert class has a bunch of static convenience methods for writing test expressions. setUp() - initialize the fixture state by overriding tearDown() - clean-up after a test by overriding A TestSuite is an object that contains an ordered list of runnable Test objects.

JUnit: Best practices Use setUp(), tearDown() and not the constructor Avoid side effects Keep tests in the mirrored directory structure of source location Use the TestRunner.run(Class c) method Testing is meant to improve the quality of the code => Don’t change a private method into a public one so you can test it Keeping old test running is just as important as making new ones run Run tests as often as possible => The earlier you detect the bug the sooner you solve it When you work on a bug, write a test case first => Your work is done when the test case succeeds