Java library for testing code with mock objects

 Mock objects help you design and test the interactions between the objects in
 your programs.
 The jMock library:
  * makes it quick and easy to define mock objects, so you don't break the
    rhythm of programming.
  * lets you precisely specify the interactions between your objects, reducing
    the brittleness of your tests.
  * works well with the autocompletion and refactoring features of your IDE
  * plugs into your favourite test framework
  * is easy to extend.