anchor.diff:  OK
   ----
   
  -Now we will change the value of our test to see when it fails : 
  +===== What happens if the test fails : 
   
   [source, python]
   ----
  
positive.code: 
  ==== Using unittest library
  
  An easy example : 
  
  [source,python]
  ----
  
negative.code:         self.assertEqual(res, 3)
  ----
  
  The output is now : 
  
  ----
  ======================================================================
  