Explain what is JUnit?

JUnit is a testing framework for unit testing.  It uses Java as a programming platform, and it is an Open Source Software managed by the JUnit.org community. It uses Java Archive package file format during compilation. The entire package framework resides under different names for different versions. For example, for JUnit 3.8, it is junit.framework package and for JUnit 4 and later, it is org.junit package.