anchor.diff:  node_debug(Line, Args) ->
       case ?NODE_DEBUG of
           true ->
  -            lager:info("~p: " ++ Line, [?MODULE|Args]);
  +            lager:info("~p: " ++ Line, [?MODULE] ++ Args);
           false ->
               ok
       end.
  
positive.code:     true;
  node_postcondition(#state{sent=Sent}, {call, ?MODULE, check_mailbox, [Node]}, {ok, Messages}) ->
      node_debug("verifying mailbox at node ~p: sent: ~p, received: ~p", [Node, Sent, Messages]),
      lists:all(fun(M) -> lists:member(M, Messages) end, Sent);
  node_postcondition(_State, _Command, _Response) ->
      false.
  
  
negative.code: %%%===================================================================
  
  message() ->
      ?LET(Id, erlang:unique_integer([positive, monotonic]), 
          ?LET(Timestamp, erlang:timestamp(),
              {Id, Timestamp})).
  
  node_name() ->
      ?LET(Names, names(), oneof(Names)).
  