anchor.diff:  Of course, we don't add the mock callback to the test suite, it's not
   a test.
   
  -For a successful compile and link, the `words.h` file must now look like...
  +For a successful compile and link, the `words.h` file must now look 
  +like...
   
   [source,c]
   ----------------------------
  
positive.code: include::tutorial_src/words_tests4.c[lines=37..43]
  ----------------------------
  
  Each call is expected in sequence. Any failures, or left-over or extra
  calls, and we get failures. We can see all this when we run the
  tests...
  
  ----------------------------
  
negative.code: === BDD Style vs. TDD Style
  
  So far we have encouraged the modern BDD style. It has merits that we
  really want you to benefit from. But you might come across *Cgreen* 
  test in another style, more like the standard TDD style, which is 
  more inline with previous thinking and might be more similar to other
  frameworks.
  
  The only difference, in principle, is the use of the SUT or
  'context'. In the BDD style you have it, in the TDD style you don't.
  