JUnit 4 - Basic for Java Interview

INTO to Junit

1. @TestMark your test cases with @Test annotations. You don’t need to prefix your test cases with “test”.  In addition, your class does not need to extend from “TestCase” class.
   @Test
   public void addition() {
   assertEquals(12, simpleMath.add(7, 5));
   }
   @Test
   public void subtraction() {
   assertEquals(9, simpleMath.substract(12, 3));
   }
2. @Before and @After
   Use @Before and @After annotations for “setup” and “tearDown” methods respectively. They run before and after every test case.
   @Before
   public void runBeforeEveryTest() {
   simpleMath = new SimpleMath();
   }
   @After
   public void runAfterEveryTest() {
   simpleMath = null;
   }
3. @BeforeClass and @AfterClassUse @BeforeClass and @AfterClass annotations for class wide “setup” and “tearDown” respectively. Think them as one time setup and tearDown. They run for one time before and after all test cases.
   @BeforeClass
   public static void runBeforeClass() {
   // run for one time before all test cases
   }
   @AfterClass
   public static void runAfterClass() {
   // run for one time after all test cases
   }
4. Exception Handling
   Use “expected” paramater with @Test annotation for test cases that expect exception. Write the class name of the exception that will be thrown.
   @Test(expected = ArithmeticException.class)
   public void divisionWithException() {
   // divide by zero
   simpleMath.divide(1, 0);
   }
5. @Ignore
   Put @Ignore annotation for test cases you want to ignore. You can add a string parameter that defines the reason of ignorance if you want.
   
   @Ignore(“Not Ready to Run”)
   @Test
   public void multiplication() {
   assertEquals(15, simpleMath.multiply(3, 5));
   }
6. Timeout
   Define a timeout period in miliseconds with “timeout” parameter. The test fails when the timeout period exceeds.
   @Test(timeout = 1000)
   public void infinity() {
   while (true)
   ;
   }
7. New Assertions
   Compare arrays with new assertion methods. Two arrays are equal if they have the same length and each element is equal to the corresponding element in the other array; otherwise, they’re not.
   public static void assertEquals(Object[] expected, Object[] actual);
public static void assertEquals(String message, Object[] expected, Object[] actual);
   @Test
   public void listEquality() {
   List expected = new ArrayList();
   expected.add(5);
   List actual = new ArrayList();
   actual.add(5);
   assertEquals(expected, actual);
   }
8. JUnit4Adapter
   Run your Junit 4 tests in Junit 3 test runners with Junit4Adapter.
   public static junit.framework.Test suite() {
   return new JUnit4TestAdapter(SimpleMathTest.class);
   }