http://toomuchcoding.blogspot.no/2012/10/simulation-of-time-consuming-actions-in.html

Slow.java

import static org.mockito.Mockito.doAnswer;

//...

	doAnswer(slowly()).when(timeConsumingExternalServiceMock).process();

//...

	private static Answer<Object> slowly() {
		return new Answer<Object>() {
			public Object answer(InvocationOnMock invocation) throws Throwable {
				// Simulation of connection to external services
				LOGGER.debug("Sleeping");
				Thread.sleep(5000);
				LOGGER.debug("Stopped Sleeping");
				return null;
			}
		};
	}