anchor.diff:  
   spawn_and_check(Fun, Num) ->
       Master = self(),
  -    ct:print("aaa ~p", [Master]),
       spawn_link(fun() ->
           Fun(),
           Master ! ok
  
positive.code:     ok;
  
  count_answers(Num, Exp) ->
      Ans = receive
                #worker_answer{id = Num, response = Response} ->
                    ct:print("xxx ~p", [Response]),
                    Response;
                  X ->
                      ct:print("zzz ~p", [X]),
                      X
            after ?REQUEST_TIMEOUT ->
                ct:print("yyy ~p", [timeout]),
                {error, timeout}
            end,
      ?assertEqual(pong, Ans),
      count_answers(Num + 1, Exp).
negative.code:     case spawn_and_check(Fun, Num - 1) of
          ok ->
              receive
                  ok -> ok
              after ?REQUEST_TIMEOUT ->
                  {error, timeout}
              end;
          E ->
              E
      end.
  
  