Why I dislike mocks

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Mock's are brittle and force your tests to assume an implementation of the code you are testing. Today, the unit test broke because I added this line of code:

            LOG.debug("Received Message " + responseMessage.getJMSCorrelationID());

The reported failure:

Testcase: testRequestSendsMessageAndWaitsForResponse(JmsServiceImplUnitTest):	Caused an ERROR

  Unexpected method call getJMSCorrelationID():
java.lang.AssertionError: 
  Unexpected method call getJMSCorrelationID():
	at org.easymock.internal.MockInvocationHandler.invoke(MockInvocationHandler.java:29)
	at org.easymock.internal.ObjectMethodsFilter.invoke(ObjectMethodsFilter.java:45)
	at $Proxy13.getJMSCorrelationID(Unknown Source)
	at JmsServiceImpl.makeRequest(JmsServiceImpl.java:48)
	at JmsServiceImplUnitTest.testRequestSendsMessageAndWaitsForResponse(JmsServiceImplUnitTest.java:56)

The fix:

expect(sendMessage.getJMSCorrelationID()).andReturn("JMS1").anyTimes();

Sorting out problems like this seems to be a complete waste of time. My preference would be to use a stub or a fake object.