JUnit is a testing framework which allows to create automated tests. The development of JUnit was started by Kent Beck and Erich Gamma in late 1995. Since then, the popularity of the framework has been growing. Nowadays, it is broadly considered as the de facto standard for testing Java applications.

JUnit was designed to be a unit-testing framework. Nevertheless, it can be used to implement not just unit tests, but also other kinds of tests. As we will discover in the body of this book, depending on how the test logic exercises the piece of software under test, a test case implemented with JUnit can be considered as an unit, integration, system, and even acceptance test. All in all, we can think of JUnit as a multi-purpose testing framework for Java.