diff --git a/apps/emqx_sn/test/emqx_sn_frame_SUITE.erl b/apps/emqx_sn/test/emqx_sn_frame_SUITE.erl
index d4500315c..813a1a343 100644
--- a/apps/emqx_sn/test/emqx_sn_frame_SUITE.erl
+++ b/apps/emqx_sn/test/emqx_sn_frame_SUITE.erl
@@ -21,6 +21,7 @@
 
 -include_lib("emqx_sn/include/emqx_sn.hrl").
 -include_lib("eunit/include/eunit.hrl").
+-define(SHOW(X), ??X).
 
 -import(emqx_sn_frame, [ parse/1
                        , serialize/1
@@ -67,6 +68,14 @@ t_willtopic(_) ->
     Wt = #mqtt_sn_message{type = ?SN_WILLTOPIC, variable = {Flags, <<"WillTopic">>}},
     ?assertEqual({ok, Wt}, parse(serialize(Wt))).
 
+t_undefined_willtopic(_) ->
+    Wt = #mqtt_sn_message{type = ?SN_WILLTOPIC},
+    ?assertEqual({ok, Wt}, parse(serialize(Wt))).
+
+t_willtopic_resp(_) ->
+    Wt = #mqtt_sn_message{type = ?SN_WILLTOPICRESP, variable = 0},
+    ?assertEqual({ok, Wt}, parse(serialize(Wt))).
+
 t_willmsgreq(_) ->
     WmReq = #mqtt_sn_message{type = ?SN_WILLMSGREQ},
     ?assertEqual({ok, WmReq}, parse(serialize(WmReq))).
@@ -88,6 +97,12 @@ t_publish(_) ->
     PubMsg = #mqtt_sn_message{type = ?SN_PUBLISH, variable = {Flags, 1, 2, <<"Payload">>}},
     ?assertEqual({ok, PubMsg}, parse(serialize(PubMsg))).
 
+t_publish_long_msg(_) ->
+    Flags = #mqtt_sn_flags{dup = false, qos = 1, retain = false, topic_id_type = 2#01},
+    Payload = generate_random_binary(256 + rand:uniform(256)),
+    PubMsg = #mqtt_sn_message{type = ?SN_PUBLISH, variable = {Flags, 1, 2, Payload}},
+    ?assertEqual({ok, PubMsg}, parse(serialize(PubMsg))).
+
 t_puback(_) ->
     PubAck = #mqtt_sn_message{type = ?SN_PUBACK, variable = {1, 2, 0}},
     ?assertEqual({ok, PubAck}, parse(serialize(PubAck))).
@@ -105,9 +120,21 @@ t_pubcomp(_) ->
     ?assertEqual({ok, PubComp}, parse(serialize(PubComp))).
 
 t_subscribe(_) ->
-    Flags = #mqtt_sn_flags{dup = false, qos = 1, topic_id_type = 16#01},
+    Flags = #mqtt_sn_flags{dup = false, qos = 1, topic_id_type = ?SN_PREDEFINED_TOPIC},
     SubMsg = #mqtt_sn_message{type = ?SN_SUBSCRIBE, variable = {Flags, 16#4321, 16}},
-    ?assertEqual({ok, SubMsg}, parse(serialize(SubMsg))).
+    ?assertEqual({ok, SubMsg}, parse(serialize(SubMsg))),
+
+    Flags1 = #mqtt_sn_flags{dup = false, qos = 1, topic_id_type = ?SN_NORMAL_TOPIC},
+    SubMsg1 = #mqtt_sn_message{type = ?SN_SUBSCRIBE, variable = {Flags1, 16#4321, <<"t/+">>}},
+    ?assertEqual({ok, SubMsg1}, parse(serialize(SubMsg1))),
+
+    Flags2 = #mqtt_sn_flags{dup = false, qos = 1, topic_id_type = ?SN_SHORT_TOPIC},
+    SubMsg2 = #mqtt_sn_message{type = ?SN_SUBSCRIBE, variable = {Flags2, 16#4321, <<"t/+">>}},
+    ?assertEqual({ok, SubMsg2}, parse(serialize(SubMsg2))),
+
+    Flags3 = #mqtt_sn_flags{dup = false, qos = 1, topic_id_type = ?SN_RESERVED_TOPIC},
+    SubMsg3 = #mqtt_sn_message{type = ?SN_SUBSCRIBE, variable = {Flags3, 16#4321, <<"t/+">>}},
+    ?assertEqual({ok, SubMsg3}, parse(serialize(SubMsg3))).
 
 t_suback(_) ->
     Flags = #mqtt_sn_flags{qos = 1},
@@ -137,6 +164,10 @@ t_disconnect(_) ->
     Disconn = #mqtt_sn_message{type = ?SN_DISCONNECT},
     ?assertEqual({ok, Disconn}, parse(serialize(Disconn))).
 
+t_disconnect_duration(_) ->
+    Disconn = #mqtt_sn_message{type = ?SN_DISCONNECT, variable = 120},
+    ?assertEqual({ok, Disconn}, parse(serialize(Disconn))).
+
 t_willtopicupd(_) ->
     Flags = #mqtt_sn_flags{qos = 1, retain = true},
     WtUpd = #mqtt_sn_message{type = ?SN_WILLTOPICUPD, variable = {Flags, <<"Topic">>}},
@@ -150,6 +181,43 @@ t_willmsgresp(_) ->
     UpdResp = #mqtt_sn_message{type = ?SN_WILLMSGRESP, variable = 0},
     ?assertEqual({ok, UpdResp}, parse(serialize(UpdResp))).
 
+t_invalid_inpacket(_) ->
+    Bin = <<2:8/big-integer, 16#F0:8/big-integer>>,
+    ?assertMatch({'EXIT', {unkown_message_type, _Stack}}, catch parse(Bin)).
+
+t_message_type(_) ->
+    TypeNames = [ {?SN_ADVERTISE, ?SHOW(SN_ADVERTISE)}
+                , {?SN_SEARCHGW, ?SHOW(SN_SEARCHGW)}
+                , {?SN_GWINFO, ?SHOW(SN_GWINFO)}
+                , {?SN_CONNECT, ?SHOW(SN_CONNECT)}
+                , {?SN_CONNACK, ?SHOW(SN_CONNACK)}
+                , {?SN_WILLTOPICREQ, ?SHOW(SN_WILLTOPICREQ)}
+                , {?SN_WILLTOPIC, ?SHOW(SN_WILLTOPIC)}
+                , {?SN_WILLMSGREQ, ?SHOW(SN_WILLMSGREQ)}
+                , {?SN_WILLMSG, ?SHOW(SN_WILLMSG)}
+                , {?SN_REGISTER, ?SHOW(SN_REGISTER)}
+                , {?SN_REGACK, ?SHOW(SN_REGACK)}
+                , {?SN_PUBLISH, ?SHOW(SN_PUBLISH)}
+                , {?SN_PUBACK, ?SHOW(SN_PUBACK)}
+                , {?SN_PUBCOMP, ?SHOW(SN_PUBCOMP)}
+                , {?SN_PUBREC, ?SHOW(SN_PUBREC)}
+                , {?SN_PUBREL, ?SHOW(SN_PUBREL)}
+                , {?SN_SUBSCRIBE, ?SHOW(SN_SUBSCRIBE)}
+                , {?SN_SUBACK, ?SHOW(SN_SUBACK)}
+                , {?SN_UNSUBSCRIBE, ?SHOW(SN_UNSUBSCRIBE)}
+                , {?SN_UNSUBACK, ?SHOW(SN_UNSUBACK)}
+                , {?SN_PINGREQ, ?SHOW(SN_PINGREQ)}
+                , {?SN_PINGRESP, ?SHOW(SN_PINGRESP)}
+                , {?SN_DISCONNECT, ?SHOW(SN_DISCONNECT)}
+                , {?SN_WILLTOPICUPD, ?SHOW(SN_WILLTOPICUPD)}
+                , {?SN_WILLTOPICRESP, ?SHOW(SN_WILLTOPICRESP)}
+                , {?SN_WILLMSGUPD, ?SHOW(SN_WILLMSGUPD)}
+                , {?SN_WILLMSGRESP, ?SHOW(SN_WILLMSGRESP)}
+                ],
+    {Types, Names} = lists:unzip(TypeNames),
+    ?assertEqual(Names, [emqx_sn_frame:message_type(Type) || Type <- Types]),
+    ok.
+
 t_random_test(_) ->
     random_test_body(),
     random_test_body(),
@@ -171,6 +239,9 @@ random_test_body() ->
 generate_random_binary() ->
     % The min packet length is 2
     Len = rand:uniform(299) + 1,
+    generate_random_binary(Len).
+
+generate_random_binary(Len) ->
     gen_next(Len, <<>>).
 
 gen_next(0, Acc) ->
@@ -178,4 +249,3 @@ gen_next(0, Acc) ->
 gen_next(N, Acc) ->
     Byte = rand:uniform(256) - 1,
     gen_next(N-1, <<Acc/binary, Byte:8>>).
-
diff --git a/apps/emqx_sn/test/emqx_sn_misc_SUITE.erl b/apps/emqx_sn/test/emqx_sn_misc_SUITE.erl
new file mode 100644
index 000000000..127cb22e3
--- /dev/null
+++ b/apps/emqx_sn/test/emqx_sn_misc_SUITE.erl
@@ -0,0 +1,62 @@
+%%--------------------------------------------------------------------
+%% Copyright (c) 2020-2022 EMQ Technologies Co., Ltd. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%--------------------------------------------------------------------
+
+-module(emqx_sn_misc_SUITE).
+
+-compile(export_all).
+-compile(nowarn_export_all).
+
+-include_lib("eunit/include/eunit.hrl").
+
+%%--------------------------------------------------------------------
+%% Setups
+%%--------------------------------------------------------------------
+
+all() ->
+    emqx_ct:all(?MODULE).
+
+init_per_suite(Config) ->
+    emqx_ct_helpers:start_apps([emqx_sn]),
+    Config.
+
+end_per_suite(_Config) ->
+    emqx_ct_helpers:stop_apps([emqx_sn]).
+
+init_per_testcase(_TestCase, Config) ->
+    Config.
+
+end_per_testcase(_TestCase, Config) ->
+    Config.
+
+%%--------------------------------------------------------------------
+%% Test cases
+%%--------------------------------------------------------------------
+t_sn_app(_) ->
+    ?assertMatch({'EXIT', {_, _}}, catch emqx_sn_app:start_listeners()),
+    ?assertMatch({error, _}, emqx_sn_app:stop_listener({udp, 9999, []})),
+    ?assertMatch({error, _}, emqx_sn_app:stop_listener({udp, {{0,0,0,0}, 9999}, []})),
+    ok.
+
+t_sn_broadcast(_) ->
+    ?assertEqual(ignored, gen_server:call(emqx_sn_broadcast, ignored)),
+    ?assertEqual(ok, gen_server:cast(emqx_sn_broadcast, ignored)),
+    ?assertEqual(ignored, erlang:send(emqx_sn_broadcast, ignored)),
+    ?assertEqual(broadcast_advertise, erlang:send(emqx_sn_broadcast, broadcast_advertise)),
+    ?assertEqual(ok, emqx_sn_broadcast:stop()).
+
+%%--------------------------------------------------------------------
+%% Helper funcs
+%%--------------------------------------------------------------------
diff --git a/apps/emqx_sn/test/emqx_sn_protocol_SUITE.erl b/apps/emqx_sn/test/emqx_sn_protocol_SUITE.erl
index 4912b4fcf..b064b630e 100644
--- a/apps/emqx_sn/test/emqx_sn_protocol_SUITE.erl
+++ b/apps/emqx_sn/test/emqx_sn_protocol_SUITE.erl
@@ -100,6 +100,17 @@ t_connect(_) ->
     send_connect_msg(Socket, <<"client_id_test1">>),
     ?assertEqual(<<3, ?SN_CONNACK, 0>>, receive_response(Socket)),
 
+    %% unexpected advertise
+    Adv = ?SN_ADVERTISE_MSG(1, 100),
+    AdvPacket = emqx_sn_frame:serialize(Adv),
+    send_packet(Socket, AdvPacket),
+    timer:sleep(200),
+
+    %% unexpected connect
+    ClientId = ?CLIENTID,
+    send_connect_msg(Socket, ClientId),
+    timer:sleep(200),
+
     send_disconnect_msg(Socket, undefined),
     ?assertEqual(<<2, ?SN_DISCONNECT>>, receive_response(Socket)),
     gen_udp:close(Socket).
@@ -412,6 +423,16 @@ t_publish_negqos_case09(_) ->
     ?assertEqual(<<2, ?SN_DISCONNECT>>, receive_response(Socket)),
     gen_udp:close(Socket).
 
+t_publish_negqos_case10(_) ->
+    QoS = ?QOS_NEG1,
+    MsgId = 1,
+    TopicId1 = ?PREDEF_TOPIC_ID1,
+    {ok, Socket} = gen_udp:open(0, [binary]),
+    Payload1 = <<20, 21, 22, 23>>,
+    send_publish_msg_normal_topic(Socket, QoS, MsgId, TopicId1, Payload1),
+    timer:sleep(100),
+    gen_udp:close(Socket).
+
 t_publish_qos0_case01(_) ->
     Dup = 0,
     QoS = 0,
@@ -1075,6 +1096,60 @@ t_will_case06(_) ->
 
     gen_udp:close(Socket).
 
+t_will_case07(_) ->
+    QoS = 1,
+    Duration = 1,
+    WillMsg = <<10, 11, 12, 13, 14>>,
+    WillTopic = <<"abc">>,
+    {ok, Socket} = gen_udp:open(0, [binary]),
+    ClientId = ?CLIENTID,
+
+    ok = emqx_broker:subscribe(WillTopic),
+
+    send_connect_msg_with_will(Socket, Duration, ClientId),
+    ?assertEqual(<<2, ?SN_WILLTOPICREQ>>, receive_response(Socket)),
+
+    %% unexpected advertise
+    Adv = ?SN_ADVERTISE_MSG(1, 100),
+    AdvPacket = emqx_sn_frame:serialize(Adv),
+    send_packet(Socket, AdvPacket),
+    timer:sleep(200),
+
+    %% unexpected connect
+    send_connect_msg(Socket, ClientId),
+    timer:sleep(200),
+
+    send_willtopic_msg(Socket, WillTopic, QoS),
+    ?assertEqual(<<2, ?SN_WILLMSGREQ>>, receive_response(Socket)),
+
+    %% unexpected advertise
+    send_packet(Socket, AdvPacket),
+    timer:sleep(200),
+
+    %% unexpected connect
+    send_connect_msg(Socket, ClientId),
+    timer:sleep(200),
+
+    send_willmsg_msg(Socket, WillMsg),
+    ?assertEqual(<<3, ?SN_CONNACK, 0>>, receive_response(Socket)),
+
+    send_pingreq_msg(Socket, undefined),
+    ?assertEqual(<<2, ?SN_PINGRESP>>, receive_response(Socket)),
+
+    % wait udp client keepalive timeout
+    timer:sleep(2000),
+
+    receive
+        {deliver, WillTopic, #message{payload = WillMsg}} -> ok;
+        Msg -> ct:print("recevived --- unex: ~p", [Msg])
+    after
+        1000 -> ct:fail(wait_willmsg_timeout)
+    end,
+    send_disconnect_msg(Socket, undefined),
+    ?assertEqual(udp_receive_timeout, receive_response(Socket)),
+
+    gen_udp:close(Socket).
+
 t_asleep_test01_timeout(_) ->
     QoS = 1,
     Duration = 1,
@@ -1960,6 +2035,7 @@ t_register_enqueue_delivering_messages(_) ->
     _ = emqx:publish(emqx_message:make(test, ?QOS_1, <<"topic-a">>, <<"m2">>)),
 
     send_regack_msg(NSocket, TopicIdA, RegMsgIdA, ?SN_RC_ACCEPTED),
+    send_regack_msg(NSocket, TopicIdA, RegMsgIdA, ?SN_RC_INVALID_TOPIC_ID),
 
     %% receive the queued messages
 
@@ -1983,6 +2059,28 @@ t_register_enqueue_delivering_messages(_) ->
     gen_udp:close(NSocket1),
     restart_emqx_sn(#{subs_resume => false}).
 
+t_code_change(_) ->
+    Old = [state, gwid, socket, socketpid, socketstate, socketname, peername,
+           channel, clientid, username, password, will_msg, keepalive_interval,
+           connpkt, asleep_timer, enable_stats, stats_timer, enable_qos3,
+           has_pending_pingresp, pending_topic_ids],
+    New = Old ++ [false, [], undefined],
+
+    OldTulpe = erlang:list_to_tuple(Old),
+    NewTulpe = erlang:list_to_tuple(New),
+
+    ?assertEqual({ok, name, NewTulpe},
+                 emqx_sn_gateway:code_change(1, name, OldTulpe, ["4.3.2"])),
+
+    ?assertEqual({ok, name, NewTulpe},
+                 emqx_sn_gateway:code_change(1, name, NewTulpe, ["4.3.6"])),
+
+    ?assertEqual({ok, name, NewTulpe},
+                 emqx_sn_gateway:code_change({down, 1}, name, NewTulpe, ["4.3.6"])),
+
+    ?assertEqual({ok, name, OldTulpe},
+                 emqx_sn_gateway:code_change({down, 1}, name, NewTulpe, ["4.3.2"])).
+
 %%--------------------------------------------------------------------
 %% Helper funcs
 %%--------------------------------------------------------------------
@@ -2267,6 +2365,9 @@ send_disconnect_msg(Socket, Duration) ->
     ?LOG("send_disconnect_msg Duration=~p", [Duration]),
     ok = gen_udp:send(Socket, ?HOST, ?PORT, DisConnectPacket).
 
+send_packet(Socket, Packet) ->
+    ok = gen_udp:send(Socket, ?HOST, ?PORT, Packet).
+
 mid(Id) -> Id.
 tid(Id) -> Id.
 
diff --git a/apps/emqx_sn/test/emqx_sn_registry_SUITE.erl b/apps/emqx_sn/test/emqx_sn_registry_SUITE.erl
index 0d726f190..5d6bb9572 100644
--- a/apps/emqx_sn/test/emqx_sn_registry_SUITE.erl
+++ b/apps/emqx_sn/test/emqx_sn_registry_SUITE.erl
@@ -108,6 +108,11 @@ t_deny_wildcard_topic(_Config) ->
     ?assertEqual({error, wildcard_topic}, ?REGISTRY:register_topic(<<"ClientId">>, <<"/TopicA/#">>)),
     ?assertEqual({error, wildcard_topic}, ?REGISTRY:register_topic(<<"ClientId">>, <<"/+/TopicB">>)).
 
+t_gen_server(_) ->
+    ?assertEqual(ignored, gen_server:call(emqx_sn_registry, ignored)),
+    ?assertEqual(ok, gen_server:cast(emqx_sn_registry, ignored)),
+    ?assertEqual(ignored, erlang:send(emqx_sn_registry, ignored)).
+
 %%--------------------------------------------------------------------
 %% Helper funcs
 %%--------------------------------------------------------------------