diff --git a/src/emqx_cm.erl b/src/emqx_cm.erl
index 3e9958939..19892b386 100644
--- a/src/emqx_cm.erl
+++ b/src/emqx_cm.erl
@@ -30,6 +30,9 @@
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2,
          code_change/3]).
 
+%% internal export
+-export([update_conn_stats/0]).
+
 -define(CM, ?MODULE).
 
 %% ETS Tables.
@@ -125,7 +128,7 @@ init([]) ->
     _ = emqx_tables:new(?CONN_TAB, [{read_concurrency, true} | TabOpts]),
     _ = emqx_tables:new(?CONN_ATTRS_TAB, TabOpts),
     _ = emqx_tables:new(?CONN_STATS_TAB, TabOpts),
-    ok = emqx_stats:update_interval(cm_stats, fun update_conn_stats/0),
+    ok = emqx_stats:update_interval(cm_stats, fun ?MODULE:update_conn_stats/0),
     {ok, #{conn_pmon => emqx_pmon:new()}}.
 
 handle_call(Req, _From, State) ->
diff --git a/src/emqx_router_helper.erl b/src/emqx_router_helper.erl
index d0d0e8075..5431c9900 100644
--- a/src/emqx_router_helper.erl
+++ b/src/emqx_router_helper.erl
@@ -31,6 +31,9 @@
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2,
          code_change/3]).
 
+%% internal export
+-export([stats_fun/0]).
+
 -record(routing_node, {name, const = unused}).
 -record(state, {nodes = []}).
 
@@ -90,7 +93,7 @@ init([]) ->
                                [Node | Acc]
                   end
               end, [], mnesia:dirty_all_keys(?ROUTING_NODE)),
-    emqx_stats:update_interval(route_stats, stats_fun()),
+    emqx_stats:update_interval(route_stats, fun ?MODULE:stats_fun/0),
     {ok, #state{nodes = Nodes}, hibernate}.
 
 handle_call(Req, _From, State) ->
@@ -143,13 +146,11 @@ code_change(_OldVsn, State, _Extra) ->
 %%------------------------------------------------------------------------------
 
 stats_fun() ->
-    fun() ->
-        case ets:info(?ROUTE, size) of
-            undefined -> ok;
-            Size ->
-                emqx_stats:setstat('routes/count', 'routes/max', Size),
-                emqx_stats:setstat('topics/count', 'topics/max', Size)
-        end
+    case ets:info(?ROUTE, size) of
+        undefined -> ok;
+        Size ->
+            emqx_stats:setstat('routes/count', 'routes/max', Size),
+            emqx_stats:setstat('topics/count', 'topics/max', Size)
     end.
 
 cleanup_routes(Node) ->
diff --git a/src/emqx_sm.erl b/src/emqx_sm.erl
index 1fa0b488b..d45548a78 100644
--- a/src/emqx_sm.erl
+++ b/src/emqx_sm.erl
@@ -31,6 +31,9 @@
 %% Internal functions for rpc
 -export([dispatch/3]).
 
+%% Internal function for stats
+-export([stats_fun/0]).
+
 %% gen_server callbacks
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2,
          code_change/3]).
@@ -210,7 +213,7 @@ init([]) ->
     _ = emqx_tables:new(?SESSION_P_TAB, TabOpts),
     _ = emqx_tables:new(?SESSION_ATTRS_TAB, TabOpts),
     _ = emqx_tables:new(?SESSION_STATS_TAB, TabOpts),
-    emqx_stats:update_interval(sm_stats, stats_fun()),
+    emqx_stats:update_interval(sm_stats, fun ?MODULE:stats_fun/0),
     {ok, #{session_pmon => emqx_pmon:new()}}.
 
 handle_call(Req, _From, State) ->
@@ -251,10 +254,8 @@ code_change(_OldVsn, State, _Extra) ->
 %%------------------------------------------------------------------------------
 
 stats_fun() ->
-    fun() ->
-        safe_update_stats(?SESSION_TAB, 'sessions/count', 'sessions/max'),
-        safe_update_stats(?SESSION_P_TAB, 'sessions/persistent/count', 'sessions/persistent/max')
-    end.
+    safe_update_stats(?SESSION_TAB, 'sessions/count', 'sessions/max'),
+    safe_update_stats(?SESSION_P_TAB, 'sessions/persistent/count', 'sessions/persistent/max').
 
 safe_update_stats(Tab, Stat, MaxStat) ->
     case ets:info(Tab, size) of
diff --git a/test/emqx_stats_tests.erl b/test/emqx_stats_tests.erl
index 5c3a9c803..dd9733a88 100644
--- a/test/emqx_stats_tests.erl
+++ b/test/emqx_stats_tests.erl
@@ -42,7 +42,7 @@ get_state_test() ->
     end).
 
 update_interval_test() ->
-    TickMs = 100,
+    TickMs = 200,
     with_proc(fun() ->
         SleepMs = TickMs * 2 + TickMs div 2, %% sleep for 2.5 ticks
         emqx_stats:cancel_update(cm_stats),
@@ -52,22 +52,34 @@ update_interval_test() ->
         ?assertEqual(1, emqx_stats:getstat('connections/count'))
     end, TickMs).
 
-emqx_broker_helpe_test() ->
-    TickMs = 100,
-    with_proc(fun() ->
-        SleepMs = TickMs + TickMs div 2, %% sleep for 1.5 ticks
-        Ref = make_ref(),
-        Tester = self(),
-        UpdFun =
-            fun() ->
-                    emqx_broker_helper:stats_fun(),
-                    Tester ! Ref,
-                    ok
-            end,
-            ok = emqx_stats:update_interval(stats_test, UpdFun),
-            timer:sleep(SleepMs),
-            receive Ref -> ok after 2000 -> error(timeout) end
-              end, TickMs).
+helper_test_() ->
+    TickMs = 200,
+    TestF =
+        fun(CbModule, CbFun) ->
+                SleepMs = TickMs + TickMs div 2, %% sleep for 1.5 ticks
+                Ref = make_ref(),
+                Tester = self(),
+                UpdFun =
+                    fun() ->
+                            CbModule:CbFun(),
+                            Tester ! Ref,
+                            ok
+                    end,
+                    ok = emqx_stats:update_interval(stats_test, UpdFun),
+                    timer:sleep(SleepMs),
+                    receive Ref -> ok after 2000 -> error(timeout) end
+        end,
+    MkTestFun =
+        fun(CbModule, CbFun) ->
+                fun() ->
+                        with_proc(fun() -> TestF(CbModule, CbFun) end, TickMs)
+                end
+        end,
+    [{"emqx_broker_helper", MkTestFun(emqx_broker_helper, stats_fun)},
+     {"emqx_sm", MkTestFun(emqx_sm, stats_fun)},
+     {"emqx_router_helper", MkTestFun(emqx_router_helper, stats_fun)},
+     {"emqx_cm", MkTestFun(emqx_cm, update_conn_stats)}
+    ].
 
 with_proc(F) ->
     {ok, _Pid} = emqx_stats:start_link(),