test(retainer): add test case for stopping publish clear msg

apps/emqx_retainer/test/emqx_retainer_SUITE.erl

@@ -195,6 +195,21 @@ t_clean(_) ->
 
     ok = emqtt:disconnect(C1).
 
+t_stop_publish_clear_msg(_) ->
+    emqx_retainer:update_config(#{<<"stop_publish_clear_msg">> => true}),
+    {ok, C1} = emqtt:start_link([{clean_start, true}, {proto_ver, v5}]),
+    {ok, _} = emqtt:connect(C1),
+    emqtt:publish(C1, <<"retained/0">>, <<"this is a retained message 0">>, [{qos, 0}, {retain, true}]),
+
+    {ok, #{}, [0]} = emqtt:subscribe(C1, <<"retained/#">>, [{qos, 0}, {rh, 0}]),
+    ?assertEqual(1, length(receive_messages(1))),
+
+    emqtt:publish(C1, <<"retained/0">>, <<"">>, [{qos, 0}, {retain, true}]),
+    ?assertEqual(0, length(receive_messages(1))),
+
+    emqx_retainer:update_config(#{<<"stop_publish_clear_msg">> => false}),
+    ok = emqtt:disconnect(C1).
+
 t_flow_control(_) ->
     emqx_retainer:update_config(#{<<"flow_control">> => #{<<"max_read_number">> => 1,
                                                           <<"msg_deliver_quota">> => 1,