Using JUnit

1. Using JUnit How we can use JUnit for testing in Bandera By Todd Wallentine (tcw@cis.ksu.edu)

2. Overview • What is JUnit? • Example Usage • Talking Points • References

3. What is JUnit? • JUnit is a regression testing framework built by Erich Gamma and Kent Beck[1]. • It can be used for regression testing as well as for simple Unit testing. • It will not work for regression testing of the GUI components. • Works very well to test methods!

4. Example • We need to test a class called Math that performs simple • operations (add, subtract, multiply, and divide). It has four • method calls: • add(int a, int b) : int • subtract(int a, int b) : int • multiply(int a, int b) : int • divide(int a, int b) : int • To exercise this class, we will create a JUnit TestCase that • will perform simple tests. • The addition of 1 and 1 will be 2. • The subtraction of 3 from 5 will be 2. • The multiplication of 2 and 2 will be 4. • The division of 10 by 2 will be 5.

5. Example (continued) To create a JUnit test, we will extend the class TestCase. public class MathTestCase extends TestCase { We will then create tests. Example for add(a, b): public void testAdd1() { int result = Math.add(1, 1); assertTrue(“1 + 1 should be 2.”, result == 2); } We will then instrument the TestCase so that all tests will be run. public static Test suite() { return(new TestSuite(MathTestCase.class)); }

6. Example – Text Output • ..F..F..F..F • Time: 0.04 • There were 4 failures: • testAdd2(math.test.MathTestCase)junit.framework.AssertionFailedError: • 1 + 1 should equal 3. result = 2 • at java.lang.Throwable.<init>(Compiled Code) • at java.lang.Error.<init>(Compiled Code) • at junit.framework.AssertionFailedError.<init>(Compiled Code) • at math.test.MathTestCase.testAdd2(Compiled Code) • 2) testSubtract2(math.test.MathTestCase)junit.framework.AssertionFailedError: • 5 - 3 should equal 3. result = 2 • at java.lang.Throwable.<init>(Compiled Code) • at java.lang.Error.<init>(Compiled Code) • at junit.framework.AssertionFailedError.<init>(Compiled Code) • at math.test.MathTestCase.testSubtract2(Compiled Code) • … [divide and multiplication errors here] … • FAILURES!!! • Tests run: 8, Failures: 4, Errors: 0

7. Example – GUI Output

8. Example – MathTestCase code public void testAdd1() { int result = Math.add(1, 1); assertTrue("1 + 1 should equal 2. result = " + result, result == 2); } public void testAdd2() { int result = Math.add(1, 1); assertTrue("1 + 1 should equal 3. result = " + result, result == 3); } public void testSubtract1() { int result = Math.subtract(5, 3); assertTrue("5 - 3 should equal 2. result = " + result, result == 2); } public void testSubtract2() { int result = Math.subtract(5, 3); assertTrue("5 - 3 should equal 3. result = " + result, result == 3); }

9. Talking Points • A good practice is to have a TestCase class for each class in a package. • A good practice is to have all TestCase classes in a subpackage, test, for each package. • A good practice is to have an all encompassing TestCase for the whole package to make regression testing easier. • JUnit will integrate into IDEs like VisualAge for Java. • A good practice is to add regression testing to the CVS submisison process so that no code gets submitted on accident that would break the regression tests.

10. References • http://junit.org • http://junit.sourceforge.net/doc/testinfected/testing.htm • http://www.junit.org/junit/doc/vaj/vaj.htm