fix(channel): unsubscribe channel listeners by equality (#3608)

backend/tests/test_channels.py

@@ -148,6 +148,27 @@ class TestMessageBus:
 
         _run(go())
 
+    def test_unsubscribe_outbound_removes_fresh_bound_method_reference(self):
+        bus = MessageBus()
+        received = []
+
+        class Handler:
+            async def callback(self, msg):
+                received.append((self, msg))
+
+        handler = Handler()
+        other_handler = Handler()
+
+        async def go():
+            bus.subscribe_outbound(handler.callback)
+            bus.subscribe_outbound(other_handler.callback)
+            bus.unsubscribe_outbound(handler.callback)
+            out = OutboundMessage(channel_name="test", chat_id="c1", thread_id="t1", text="reply")
+            await bus.publish_outbound(out)
+            assert received == [(other_handler, out)]
+
+        _run(go())
+
     def test_outbound_error_does_not_crash(self):
         bus = MessageBus()