JUnit is a unit testing framework, which played an important role in the development of test-driven development frameworks. The power of JUnit is to reach almost every single statement in your Java program, including conditional statements. It uses annotations to ensure the target method of a Java class gets executed on the selected objects during test execution.

JUnit has been important in the development of test-driven development. JUnit is linked as a JAR at compile-time and can be used to write repeatable tests.