# Support setting the loop\_factory in IsolatedAsyncioTestCase

**URL:** <https://discuss.python.org/t/support-setting-the-loop-factory-in-isolatedasynciotestcase/36027>\
**Category:** Async-SIG\
**Created:** [October 12, 2023, 10:38am UTC](https://discuss.python.org/t/support-setting-the-loop-factory-in-isolatedasynciotestcase/36027 "2023-10-12T10:38:03Z")\
**Posts on this page:** 1\
**Showing post:** 1

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**Author:** ![graingert](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/graingert/32/26847_2.png) [@graingert](https://discuss.python.org/u/graingert)\
**Post date:** [October 12, 2023, 10:38am UTC](https://discuss.python.org/t/support-setting-the-loop-factory-in-isolatedasynciotestcase/36027/1 "2023-10-12T10:38:03Z")

</div>

I want to be able to create utility subclasses of `IsolatedAsyncioTestCase` that use either uvloop or a specific event loop using the `asyncio.Runner(..., loop_factory=...)` kwarg, Ideally it would look something like:

Another advantage of setting `loop_factory` would allow use of `IsolatedAsyncioTestCase` without using `def tearDownModule(): asyncio.set_event_loop_policy(None)` because `asyncio.Runner` does not call `asyncio.get_event_loop_policy()` when called with a `loop_factory`

```auto
class DefaultIsolatedAsyncioTestCase:
    """
    Use the most efficient event loop regardless of what has been configured with asyncio.set_event_loop_policy
    does not require `def tearDownModule(): asyncio.set_event_loop_policy(None)`
    """
    loop_factory = (
        asyncio.ProactorEventLoop
        if sys.platform == "win32"
        else asyncio.SelectorEventLoop
    )

```

or

```auto
class UvloopIsolatedAsyncioTestCase:
    """
    runs tests on uvloop
    """
    loop_factory = uvloop.new_event_loop

```

the patch to CPython would look like this:

```patch
diff --git a/Lib/unittest/async_case.py b/Lib/unittest/async_case.py
index bd2a471156..beeb7037d9 100644
--- a/Lib/unittest/async_case.py
+++ b/Lib/unittest/async_case.py
@@ -32,6 +32,8 @@ class IsolatedAsyncioTestCase(TestCase):
     # should reset a policy in every test module
     # by calling asyncio.set_event_loop_policy(None) in tearDownModule()
 
+ loop_factory = None
+
     def __init__ (self, methodName='runTest'):
         super(). __init__ (methodName)
         self._asyncioRunner = None
@@ -118,7 +120,7 @@ def _callMaybeAsync(self, func, /, *args, **kwargs):
 
     def _setupAsyncioRunner(self):
         assert self._asyncioRunner is None, 'asyncio runner is already initialized'
- runner = asyncio.Runner(debug=True)
+ runner = asyncio.Runner(debug=True, loop_factory=self.loop_factory)
         self._asyncioRunner = runner
 
     def _tearDownAsyncioRunner(self):

```

---

_[View the full topic](https://discuss.python.org/t/support-setting-the-loop-factory-in-isolatedasynciotestcase/36027)._