Test Java code using mock objects

jMock is a library for testing Java code using mock objects. Mock
   objects help you design and test the interactions between the
   objects in your programs. The jMock package: * makes it quick and
   easy to define mock objects, so you don't break the rhythm of
   programming.

* lets you define flexible constraints over object interactions,
   reducing the brittleness of your tests.

* is easy to extend.