JUnit 4 – testing for exception, execution time and disabling a test

In my last post about Getting Started with JUnit 4, I talked about the basic concepts of JUnit testing framework and how to write a test case using JUnit 4. In this post, I’ll write about some tips and strategies for using JUnit effectively. We will start with JUnit annotation @Ignore.

Temporarily disabling a JUnit test:

In JUnit 4, it is possible to temperorily disable a test using the annotation @Ignore. This technique is very useful in scenarios where you are not done with that particular test case, but still want to run the other tests that are present in that test suite/class. The test methods which are annotated with both @Test and @Ignore will be ignored by the test runner. See the example below for a clear understanding.

@Test
public void testSomeMethod(){
        System.out.println("T'll be called");
}

@Ignore
@Test
public void testSomeOtherMethod(){
        System.out.println("T'll be ignored");
}

Testing for a specific Exception in JUnit testing method:

Suppose you want to check for a specific exception thrown by your testing method, you can use the expected option of @Test annotation. You can mention the Exception type that you expect the testing method to throw in the ‘expected’ option. If the method throws the exception then test is considered as passed, otherwise the test will be considered as failed.

@Test(expected=IllegalArgumentException.class)
public void testSomeMethod(){
   myObj.someMethod();
}

Testing for execution time of your method:

If you want to check if your testing method takes too long to execute, you can do that by mentioning your expected execution time using timeout option of @Test annotation. If your testing method takes longer than the time you mentioned, then the test will be considred as failed. The time is measured in milliseconds. Below is a code snippet for this.

@Test(timeout=2000)
public void testSomeMethod(){
   myObj.someMethod();
}

That’s for now. I hope that the above tips will help you t write effective JUnit tests. Feel free to share any other tips on JUnit. I’ll happy to hear from you.