To improve quality of an application, it is a good practice to provide unit tests together with the code which is written. This makes it easier to determine the impact of changes and fix them early during development.
Writing unit tests can be challenging. Often applications run inside an application server which provides services and a unit test runs outside of the server. Applications can depend on the services provided by the application server which makes testing outside of this scope difficult. One of those services is JNDI. JNDI makes it possible for an application to look up for example a datasource. Luckily JNDI can be provided outside of application server scope.
To make mocking methods in unit tests easier, the Mockito framework (https://code.google.com/p/mockito/) can be used. Mockito however uses a subclassing mechanism which does not work when dealing with final classes. Also static and private methods cannot be mocked because of this. PowerMock provides solutions for those issues; https://code.google.com/p/powermock/.