The following example shows how we can test application component that has DAO (heavy weight) dependency using jmock objects and web layer (Controller) using spring mock api

gistfile1.java

@RunWith(JMock.class)
public class HomeControllerTest {

	Mockery context = new JUnit4Mockery();
	//mock object : ContactDAO (using JMock)
	ContactDAOInterface contactDAO = context.mock(ContactDAOInterface.class);
	// Spring MVC controller
	HomeController cc = new HomeController();
	// mock objects (using spring mock)
	private MockHttpServletRequest request;
	private MockHttpServletResponse response;

	@Before
	public void init() throws Exception
	{
		cc.setContactDAO(contactDAO);
		// mock objects created
		request = new MockHttpServletRequest();
		response = new MockHttpServletResponse();
	}

	@Test
	public void HomePage() throws Exception
	{
		// define expectations for mock object
		context.checking(new Expectations() {{
			ArrayList<ContactData> data = new ArrayList<ContactData>();
			data.add(new ContactData(1,"Abdul Aziz","07525776781"));
	        oneOf (contactDAO).getContacts(); will(returnValue(data));
	    }});

		// test
		request.setMethod("GET");
		ModelAndView mav= cc.handleRequest(request, response);
		Assert.assertEquals("viewContacts", mav.getViewName());
		ArrayList<ContactData> obj=(ArrayList<ContactData>)mav.getModel().get("contacts");
		Assert.assertNotNull(obj);
		Assert.assertEquals(1,obj.size());
		Assert.assertEquals("Abdul Aziz",obj.get(0).getName());
		Assert.assertEquals("07525776781",obj.get(0).getPhone());
	}
}

http://j2eeroad.wordpress.com/2010/02/07/testing-using-junit-4-jmock-spring-mock/