To be continued from the previous articles, I would like to introduce you a free application for Android named Learn JUnit JUnit is a unit testing framework for the Java programming language. JUnit has been important in the development of test-driven development, and is one of a family of unit testing frameworks collectively known as xUnit that originated with JUnit. This app will teach you how to use JUnit in your day-2-day life of any project unit testing while working with Java programming language.