Improve coverage

test/emqx_packet_SUITE.erl

@@ -46,7 +46,12 @@ packet_type_name(_) ->
 packet_validate(_) ->
     ?assertEqual(true, emqx_packet:validate(?SUBSCRIBE_PACKET(15, #{'Subscription-Identifier' => 1}, [{<<"topic">>, #{qos => ?QOS0}}]))),
     ?assertEqual(true, emqx_packet:validate(?UNSUBSCRIBE_PACKET(89, [<<"topic">>]))),
-    ?assertEqual(true, emqx_packet:validate(?CONNECT_PACKET(#mqtt_packet_connect{}))).
+    ?assertEqual(true, emqx_packet:validate(?CONNECT_PACKET(#mqtt_packet_connect{}))),
+    ?assertEqual(true, emqx_packet:validate(?CONNECT_PACKET(#mqtt_packet_connect{properties = #{'Receive-Maximum' => 1}}))),
+    case catch emqx_packet:validate(?CONNECT_PACKET(#mqtt_packet_connect{properties = #{'Receive-Maximum' => 0}})) of
+        {'EXIT', {protocol_error, _}} -> ?assertEqual(true, true);
+        true -> ?assertEqual(true, false)
+    end.
 
 packet_message(_) ->
     Pkt = #mqtt_packet{header = #mqtt_packet_header{type   = ?PUBLISH,