anchor.diff:  %% - 2xx response is received
   %% - 2xx response is provided to the TU
   %% - transaction terminates
  +%% @end
   client_invite_ok(Transport) ->
       register(?REGNAME, self()),
   
  
positive.code: %% - 2xx response is received
  %% - 2xx response is provided to the TU
  %% - transaction terminates
  client_ok(Transport) ->
      register(?REGNAME, self()),
  
  
negative.code:     unregister(?REGNAME),
      ok.
  
  %% @doc
  %% Scenario tested:
  %% - client non-INVITE transaction is created (')
  %% - provisional response is received
  