Explain who should use JUnit – a developer or tester? Why you use JUnit to test your code?

JUnit is more often used by developers to implement unit tests in JAVA.  It is designed for unit testing that is more a coding process and not a testing process. However, many testers and QA engineers use JUnit for unit testing.
JUnit is used because

• It test early and does automate testing.
• JUnit tests can be compiled with the build so that at unit level, regression testing can be done.
• It allows test code re-usage.
• JUnit tests behave as a document for the unit tests when there is a transfer.