I like the most that it has huge stack overflow community to help you out. we can verify any interactions and stub our method calls. Using mockito in your existing project is the most easy job.

One of the best frameworks out there to create Mock objects to enable testing. Decouples the testing logic from the implementation, making it easier to write clean test cases. Ability to easily mock almost any object as per the requirements. No need to write mock objects on your own. Easiest solution out of the box to support such requirements. One of the biggest challenges with any testing/mocking framework is the support for refactoring. In Mockito renaming interface method names or reordering parameters will not break the test code as mocks are created at runtime. Those who work with Junits are well familiar that returning values is a very difficult or tedious task. Mockito however supports return values out of the box. Another blessing is the support for exceptions and ability to easily handle them. Also supports check on order of method calls. As we get more and more advanced in terms of Java, use of annotations is a great benefit to get rid of the boiler plate code. Mockito supports creating mocks using annotation.

It's possible to test a lot fo conditions and it's easy to read. Just need to know what's happening inside. Once you learn it, it's clear.