test(takeover): randomize messages for random natural ordering

apps/emqx/test/emqx_takeover_SUITE.erl

@@ -160,4 +160,15 @@ assert_messages_order([Msg | Ls1], [{publish, #{payload := No}} | Ls2]) ->
     end.
 
 messages(Cnt) ->
-    [emqx_message:make(ct, 1, ?TOPIC, integer_to_binary(I)) || I <- lists:seq(1, Cnt)].
+    [emqx_message:make(ct, 1, ?TOPIC, payload(I)) || I <- lists:seq(1, Cnt)].
+
+payload(I) ->
+    % NOTE
+    % Introduce randomness so that natural order is not the same as arrival order.
+    iolist_to_binary(
+        io_lib:format("~4.16.0B [~B] [~s]", [
+            rand:uniform(16#10000) - 1,
+            I,
+            emqx_utils_calendar:now_to_rfc3339(millisecond)
+        ])
+    ).