Update event_loop to explicitly set scope session

As recommended by the deprecation warning

Signed-off-by: Mathias L. Baumann <[email protected]>

pyproject.toml

@@ -165,6 +165,7 @@ disable = [
 [tool.pytest.ini_options]
 testpaths = ["tests", "src"]
 asyncio_mode = "auto"
+asyncio_default_fixture_loop_scope = "function"
 required_plugins = ["pytest-asyncio", "pytest-mock"]
 
 [tool.mypy]

tests/test_mananging_actor.py

@@ -9,7 +9,6 @@
 from typing import AsyncIterator, Iterator
 
 import async_solipsism
-import pytest
 import time_machine
 from frequenz.channels import Broadcast, Receiver, Sender
 from frequenz.client.dispatch.test.generator import DispatchGenerator
@@ -20,11 +19,12 @@
 from frequenz.dispatch import Dispatch, DispatchManagingActor, DispatchUpdate
 
 
-# This method replaces the event loop for all tests in the file.
-@pytest.fixture
+@fixture
 def event_loop_policy() -> async_solipsism.EventLoopPolicy:
-    """Return an event loop policy that uses the async solipsism event loop."""
-    return async_solipsism.EventLoopPolicy()
+    """Set the event loop policy to use async_solipsism."""
+    policy = async_solipsism.EventLoopPolicy()
+    asyncio.set_event_loop_policy(policy)
+    return policy
 
 
 @fixture