Python unit testing: How to stop gevent.monkey.patch_all() affecting asyncio tests? - python-asyncio

Question

We have a python test suite that tests code that uses gevent.monkey.patch_all(). The tests run fine.
In the same code base we have an alternative entrypoint that uses asyncio. There are also tests for this, which run fine on their own, with this kind of setup:
import asyncio
from our_module import main
class AsyncioTests(unittest.TestCase):
"""Test some asyncio stuff."""
def test_something(self):
asyncio.run(main())
However, if they run after the tests that import the module with the monkey patching, they hang forever. It seems to be because of the monkey patching.
Is there a way to stop this, by reversing the monkey patching?

Answer 1

I found this https://emptysqua.re/blog/undoing-gevents-monkey-patching/ via Gevent monkey unpatch but the suggestion didn't work. Seemingly the problem is a bit deeper than the one module, perhaps specifically related to asyncio, (I also tried reloading several).
However, there is an undocumented but public variable in the gevent.monkey module called saved:
# maps module name -> {attribute name: original item}
# e.g. "time" -> {"sleep": built-in function sleep}
# NOT A PUBLIC API. However, third-party monkey-patchers may be using
# it? TODO: Provide better API for them.
saved = {}
Using this, I could undo all the patches that gevent introduced in the tearDownClass of the test suite that uses that code:
class SomeTests(unittest.TestCase):
"""Tests using code imported from a module gevent.monkey.patch_all'd."""
#classmethod
def tearDownClass(cls):
"""Undo monkeypatching so that other tests don't get stuck.
Note: this is needed because of asyncio.
"""
import importlib
from gevent import monkey
for modname in monkey.saved.keys():
try:
mod = __import__(modname)
importlib.reload(mod)
for key in monkey.saved[modname].keys():
setattr(mod, key, monkey.saved[modname][key])
except ImportError:
pass
Pretty horrid...? Maybe...