Writing JUnit tests for Java classes in Eclipse and Netbeans IDE is super easy, and I will show you that later in this JUnit tutorial. Before that, let’s revise what is a unit test and why should you write them. A unit test is to test a smaller unit of code, e.g. methods. Writing a unit test to test the individual unit of code is one of the best development practices and helps to find bug earlier in the development cycle. Though there is another unit testing framework available in Java e.g. TestNG, JUnit has its own place among Java developers. IMHO code review and unit testing are two most important practices for improving code quality and should always be followed during software development.