JUnit is a unit-testing open-source framework for the Java programming language. Java Developers use this framework to write and execute automated tests. In Java, there are test cases that have to be re-executed every time a new code is added. This is done to make sure that nothing in the code is broken.

Unit testing, as the name suggests, refers to the testing of small segments of code. Here, a unit indicates the smallest bit of code that can be fetched out of the system. This small bit can be a line of code, a method, or a class. The smaller the chunk of code, the better it is, as smaller chunks will tend to run faster. And this provides a better insight into the code and its performance.

JUnit is used for unit testing. And it is used for other types of testing as well. It supports the test to run by writing and testing along. JUnit framework was initially based on the SUnit framework used for Unit testing but then later it was updated with Java using Selenium WebDriver. JUnit is now used as a standard when we need to perform testing in Java.