Ensure ComponentPoolStatusTracker is stopped properly

If the test raised an exception in the middle of the test, the
`ComponentPoolStatusTracker` was not stopped, which caused the
`ComponentPoolStatusTracker` to keep running and entering a restart loop
when the asyncio event loop was closed.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

tests/microgrid/power_distributing/_component_status/test_battery_pool_status.py

@@ -3,6 +3,7 @@
 """Tests for BatteryPoolStatus."""
 
 import asyncio
+from contextlib import AsyncExitStack
 from datetime import timedelta
 
 from frequenz.channels import Broadcast
@@ -37,7 +38,8 @@ async def test_batteries_status(self, mocker: MockerFixture) -> None:
         mock_microgrid = MockMicrogrid(grid_meter=True, mocker=mocker)
         mock_microgrid.add_batteries(3)
 
-        async with mock_microgrid:
+        async with AsyncExitStack() as stack:
+            await stack.enter_async_context(mock_microgrid)
             batteries = {
                 battery.component_id
                 for battery in mock_microgrid.mock_client.component_graph.components(
@@ -55,6 +57,7 @@ async def test_batteries_status(self, mocker: MockerFixture) -> None:
                 max_blocking_duration=timedelta(seconds=30),
                 component_status_tracker_type=BatteryStatusTracker,
             )
+            stack.push_async_callback(batteries_status.stop)
             await asyncio.sleep(0.1)
 
             expected_working: set[ComponentId] = set()
@@ -123,5 +126,3 @@ async def test_batteries_status(self, mocker: MockerFixture) -> None:
                 ComponentId(9),
                 ComponentId(19),
             }
-
-            await batteries_status.stop()