anchor.diff:  
   -ifdef(TEST).
   
  +handle_packet_test_() ->
  +    EmptyState = #state{counters=maps:new(),
  +                        timers=maps:new(),
  +                        gauges=maps:new(),
  +                        sets=maps:new()},
  +    HandleSuccess = fun(P) ->
  +                            case handle_packet(P, EmptyState) of
  +                                {ok, _} -> ok;
  +                                error -> error
  +                            end
  +                    end,
  +    [?_assertEqual(ok, HandleSuccess(<<"foo">>)),
  +     ?_assertEqual(ok, HandleSuccess(<<"foo:2">>)),
  +     ?_assertEqual(ok, HandleSuccess(<<"foo:2.0|c">>)),
  +     ?_assertEqual(ok, HandleSuccess(<<"foo:2.0|c|@0.2">>)),
  +     ?_assertEqual(ok, HandleSuccess(<<"foo:2.0|c|@0.2\nfoo:5.2">>)),
  +     ?_assertEqual(ok, HandleSuccess(<<"foo:-23|c">>)),
  +     ?_assertEqual(ok, HandleSuccess(<<"foo:2.0|ms|@0.1">>)),
  +     ?_assertEqual(ok, HandleSuccess(<<"foo:223.3|g">>)),
  +     ?_assertEqual(ok, HandleSuccess(<<"foo:223.3|g|@1">>)),
  +     ?_assertEqual(ok, HandleSuccess(<<"foo:+12|g">>)),
  +     ?_assertEqual(ok, HandleSuccess(<<"foo:-9.2|g">>)),
  +     ?_assertEqual(ok, HandleSuccess(<<"foo:23.0|s">>)),
  +     ?_assertEqual(error, HandleSuccess(<<"foo:gsh">>)),
  +     ?_assertEqual(error, HandleSuccess(<<"foo:gsh|c">>)),
  +     ?_assertEqual(error, HandleSuccess(<<"foo:gsh|c|@0.1">>)),
  +     ?_assertEqual(error, HandleSuccess(<<"foo:123|t">>)),
  +     ?_assertEqual(error, HandleSuccess(<<"foo:+|g">>)),
  +     ?_assertEqual(error, HandleSuccess(<<"foo:123|c|@g">>)),
  +     ?_assertEqual(error, HandleSuccess(<<"foo:123|c|@1|x">>))
  +    ].
  +
  +
   calculate_timer_test_() ->
       [?_assertEqual({0, 0, 0, 0, 0, 0, 0}, calculate_timer([])),
        ?_assertEqual({0, 100, 100/2, 100/2, 5000.0, 100, 10000}, calculate_timer([100, 0])),
  
positive.code:     end.
  
  
  handle_metric(State, Metric) ->
      handle_metric(State, Metric, {ok, 1}, <<"c">>, {ok, 1}).
  
  
negative.code: handle(Packet, State) ->
      lager:debug("handle UDP packet: ~p", [Packet]),
  
      case handle_packet(Packet, State) of
          {ok, Updated} ->
              statser_instrumentation:increment(<<"udp.handled-values">>),
              Updated;
  