title: Replace spring bean in one context with mock version from another context
body: <p>I'm writing an integration test where an application context xml is initialized during startup. There are several test methods in the test class which make use of a specific bean 'X'(already defined in the xml). My actual requirement is to mock bean X only for one of the test methods. </p>
  
  <p>Inside a test method: I tried creating a separate application context using ClassPathXMLApplicationContext with only the mock bean 'M'. </p>
  
  <p>Now I have two Application Contexts (AC): 
  1. One created during test case startup (which contains the actual bean X) and 
  2. One created using ClassPathXMLApplicationContext within the test method (which has the mock bean M).</p>
  
  <p>I want to replaced the actual bean definition 'X' within AC:1, using the mock bean definition 'M' from AC:2.</p>
  
  <p>Can somebody throw some light on this please?</p>