test(wecom): cover SDK compatibility fallback in shutdown (#4788)

References #4762

Co-authored-by: icn5381 <255778606+icn5381@users.noreply.github.com>

backend/tests/test_channels.py

@@ -7176,6 +7176,72 @@ class TestWeComChannel:
 
         _run(go())
 
+    def test_stop_uses_sync_disconnect_fallback_without_sdk_async_helpers(self):
+        """A client that exposes neither ``_ws_manager`` (and therefore no
+        ``_async_disconnect`` / ``_stop_heartbeat`` / ``_clear_pending_messages``)
+        nor an awaitable ``disconnect()`` takes the compatibility fallback:
+        ``disconnect()`` is invoked once and ``stop()`` still clears its
+        lifecycle references."""
+        from app.channels.wecom import WeComChannel
+
+        async def go():
+            channel = WeComChannel(MessageBus(), config={})
+            disconnect_called = asyncio.Event()
+            ws_task = asyncio.create_task(asyncio.sleep(0))
+            await ws_task
+
+            class LegacySyncSDKClient:
+                def disconnect(self) -> None:
+                    disconnect_called.set()
+
+            client = LegacySyncSDKClient()
+            channel._running = True
+            channel._ws_client = client
+            channel._ws_task = ws_task
+
+            await channel.stop()
+
+            assert disconnect_called.is_set()
+            assert channel._ws_client is None
+            assert channel._ws_task is None
+            assert channel._ws_shutdown_task is None
+
+        _run(go())
+
+    def test_stop_awaits_awaitable_disconnect_fallback(self):
+        """A client whose ``disconnect()`` returns an awaitable (but has no
+        ``_ws_manager``) takes the fallback path and ``stop()`` waits for that
+        awaitable to finish before clearing its lifecycle references."""
+        from app.channels.wecom import WeComChannel
+
+        async def go():
+            channel = WeComChannel(MessageBus(), config={})
+            disconnect_called = asyncio.Event()
+            disconnect_finished = asyncio.Event()
+            ws_task = asyncio.create_task(asyncio.sleep(0))
+            await ws_task
+
+            class AwaitableSDKClient:
+                async def disconnect(self):
+                    disconnect_called.set()
+                    await asyncio.sleep(0)
+                    disconnect_finished.set()
+
+            client = AwaitableSDKClient()
+            channel._running = True
+            channel._ws_client = client
+            channel._ws_task = ws_task
+
+            await channel.stop()
+
+            assert disconnect_called.is_set()
+            assert disconnect_finished.is_set()
+            assert channel._ws_client is None
+            assert channel._ws_task is None
+            assert channel._ws_shutdown_task is None
+
+        _run(go())
+
     def test_concurrent_start_waits_for_stop_before_installing_new_client(self, monkeypatch):
         from app.channels.wecom import WeComChannel