Service node ends its call when the loop cancels every task; test order and timing leaks

_serve_once treated a cancelled call future as finished, so an event loop
cancelling all tasks at once (shutdown) never sent the worker a cancel and the
call's thread kept asyncio.run waiting for SILENCE_S. The cameras audio test
now removes its voice flow and device, the unpaired-frame test waits for its
first frame before the unpair, and test_connector no longer inherits the
controller an app test bound to demand.

Claude-Session: https://claude.ai/code/session_01SSi5AvZ7pFmySK8zy3NPMh

backend/tests/api/routes/test_cameras.py

@@ -102,6 +102,31 @@ def camera(client: TestClient, superuser_token_headers: dict[str, str]):
     client.delete(f"{PREFIX}/cam1", headers=superuser_token_headers)
 
 
+@pytest.fixture
+def microphone(client: TestClient, superuser_token_headers: dict[str, str]):
+    """A paired device with a microphone, wired in flow ``voice``. Yields its header.
+
+    Both go again afterwards: a published flow outlives the module in the
+    flow store, and the next module's app would load it without its device.
+    """
+    _panels(client, superuser_token_headers, {"panels": [{"id": "mic1"}]})
+    device = _pair(client, superuser_token_headers, "mic1")
+    port = {"port": "mic", "direction": "in", "dtype": "audio"}
+    reported = client.put(
+        f"{PREFIX}/mic1/report", headers=device, json={**REPORT, "ports": [port]}
+    )
+    assert reported.status_code == 200, reported.text
+    node = _device_node(
+        "mic1",
+        node="panel",
+        provides=[{"name": "mic", "port": "mic", "dtype": "audio"}],
+    )
+    _publish_flow(client, superuser_token_headers, "voice", [node])
+    yield device
+    client.delete(f"{FLOWS}/voice", headers=superuser_token_headers)
+    client.delete(f"{PREFIX}/mic1", headers=superuser_token_headers)
+
+
 def _ticket(client: TestClient, headers: dict[str, str]) -> str:
     answer = client.post(f"{settings.API_V1_STR}/flows/ws-ticket", headers=headers)
     return f"{SOCKET}?ticket={answer.json()['ticket']}"
@@ -269,24 +294,11 @@ def test_an_unpaired_device_is_closed_and_its_frames_stop(
 
 
 def test_a_device_streams_audio_chunks_on_its_socket(
-    client: TestClient, superuser_token_headers: dict[str, str]
+    client: TestClient, microphone
 ) -> None:
     """A microphone's chunks take the camera's path, in their own family."""
-    _panels(client, superuser_token_headers, {"panels": [{"id": "mic1"}]})
-    device = _pair(client, superuser_token_headers, "mic1")
-    port = {"port": "mic", "direction": "in", "dtype": "audio"}
-    reported = client.put(
-        f"{PREFIX}/mic1/report", headers=device, json={**REPORT, "ports": [port]}
-    )
-    assert reported.status_code == 200, reported.text
-    node = _device_node(
-        "mic1",
-        node="panel",
-        provides=[{"name": "mic", "port": "mic", "dtype": "audio"}],
-    )
-    _publish_flow(client, superuser_token_headers, "voice", [node])
     controller = client.app.state.flow_controller
-    with client.websocket_connect(SOCKET, headers=device) as ws:
+    with client.websocket_connect(SOCKET, headers=microphone) as ws:
         ws.receive_json()
         ws.send_bytes(frame("voice.mic", b"\x00\x01"))  # an image on an audio port
         ws.send_bytes(frame("voice.mic", b"\x00\x02", "audio/L16;rate=16000"))
@@ -329,9 +341,13 @@ def test_an_unpaired_device_is_closed_at_its_next_frame(
     """Without the event an unpair sends, which a full queue may have lost."""
     from starlette.websockets import WebSocketDisconnect
 
+    controller = client.app.state.flow_controller
     with client.websocket_connect(SOCKET, headers=camera) as device:
         device.receive_json()
         device.send_bytes(frame("cams.camera", b"\xff\xd8 one"))
+        # The credential is asked as each frame is read, so a bump before the
+        # server has read the first one would refuse that one too.
+        wait_for(lambda: (controller.values().get("cams.camera") or {}).get("value"))
         client.app.state.device_store.bump("cam1")
         device.send_bytes(frame("cams.camera", b"\xff\xd8 two"))
         with pytest.raises(WebSocketDisconnect) as closed:
@@ -339,7 +355,7 @@ def test_an_unpaired_device_is_closed_at_its_next_frame(
                 device.receive_json()
         assert closed.value.code == 1008
     store = client.app.state.artifact_store
-    current = client.app.state.flow_controller.values()["cams.camera"]["value"]
+    current = controller.values()["cams.camera"]["value"]
     assert store.volatile.get(current["digest"]) == b"\xff\xd8 one"