A small mock library that is extremely easy to learn with plenty of examples. Only has 5 classes for the api. This library's best feature is being able to test a 24 hour timer in milliseconds with a mockobject timer.
Java mocking is dominated by expect-run-verify libraries like EasyMock or jMock. Mockito offers simpler and more intuitive approach: you ask questions about interactions after execution. Using mockito, you can verify what you want. Using expect-run-verify libraries you are often forced to look after irrelevant interactions.
SevenMock is a light-weight Java dynamic mock objects framework. It is unusual in that it places responsibility for verifying operation parameters directly on the unit test code. This enables the test designer to write very clear, precisely targeted tests and makes test failures easier to diagnose.
RMock 2.0.0 is a Java mock object framework to use with jUnit. RMock has support for a setup-modify-run-verify workflow when writing jUnit tests. It integrates better with IDE refactoring support and allows designing classes and interfaces in a true test-first fashion.