title: What is the difference between mocking and spying when using Mockito?
body: <p>What would be a use case for a use of a Mockito spy?</p>
  
  <p>It seems to me that every spy  use case can be handled with a mock, using callRealMethod.</p>
  
  <p>One difference I can see is if you want most method calls to be real, it saves some lines of code to use a mock vs. a spy. Is that it or am I missing the bigger picture?</p>