View source for Why I dislike mocks

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:
<pre>
            LOG.debug("Received Message " + responseMessage.getJMSCorrelationID());
</pre>

The reported failure:
<pre>
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)
</pre>

The fix:
<pre>
expect(sendMessage.getJMSCorrelationID()).andReturn("JMS1").anyTimes();
</pre>

Sorting out problems like this seems to be a complete waste of time. My preference would be to use a [http://www.martinfowler.com/bliki/TestDouble.html stub or a fake object].

[[Category:Java]]