Annotations, a form of metadata, provide data about a program that is not part of the program itself. Annotations have no direct effect on the operation of the code they annotate. Annotations have been a powerful part of Java, but most times we tend to use them rather than create them.
JUnit is a unit testing framework for the Java programming language. JUnit is used primarily to test each and every unit or component of your application, like classes and methods. It helps to write and run repeatable automated tests to ensure your code runs as intended.