Although JUnit is being projected as a standard in testing java code but still there are many Java developers who have not used it. One reason is lack of practical tutorials with examples. In this tutorial, I have attempted to present Junit usage in practical way with actual examples. There is lot more that you can do with JUnit (beyond this tutorial) but it will kick start you well, I believe.

Okay, let?s proceed.

Let's Use JUnit

First obvious question, why to use JUnit when we can write a main() method to test individual methods of a class?

Answer to this is ?better management?. If you write calls to individual methods in main() method, you will have to write a lot of code to reach where you want to reach. Here?s a list of points:

1. If one method call fails, next method calls won?t be executed. You will have to work-around this.
2. Generally, you will execute main() of a class only when you are creating the class (that?s a bad habit though). If you want to execute main() of every class, every time code is changed, you will have to provide support for this yourself.
3. If you want the test results to be displayed in a GUI, you will have to write code for that GUI.
4. If you want to log the results of tests in HTML format or text format, you will have to write additional code.
5. Your classes will be cluttered with test code in main method.
6. If you start working on a project created by some other team in your organization, you may see an entirely different approach for testing. That will increase your learning time and things won?t be standard.

 Above are some of the problems, which will be taken care of automatically if you use Junit. Junit provides a standard framework for writing your tests. It separates test code from project code, hence keeps everything clean.

Let?s now move forward to learning its usage.