[Async-sig] no current event loop in thread 'MainThread'

7 Jul 2017

      I am trying to write a test for a function that uses async. Can I mix
using unittest.TestCase and asyncio.test_utils.TestCase? When I do
that, the loop in test_utils.TestCase seems to affect the other code I
have. This is a simplified example -

$ cat foo.py
import asyncio
import unittest

from asyncio import test_utils

async def foo():
    return True

class Foo1Test(test_utils.TestCase):

    def setUp(self):
        super().setUp()
        self.loop = self.new_test_loop()
        self.set_event_loop(self.loop)

    def test_foo(self):
        res = self.loop.run_until_complete(foo())
        assert res is True

class Foo2Test(unittest.TestCase):

    def test_foo(self):
        loop = asyncio.get_event_loop()
        res = loop.run_until_complete(foo())
        assert res is True

$ python3
Python 3.6.1 (default, Apr  4 2017, 09:40:21)
[GCC 4.2.1 Compatible Apple LLVM 8.1.0 (clang-802.0.38)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
...
...
...
$ python3 -m unittest foo.py
.E
======================================================================
ERROR: test_foo (foo.Foo2Test)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/private/tmp/foo.py", line 26, in test_foo
    loop = asyncio.get_event_loop()
  File "/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncio/events.py",
line 678, in get_event_loop
    return get_event_loop_policy().get_event_loop()
  File "/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncio/events.py",
line 584, in get_event_loop
    % threading.current_thread().name)
RuntimeError: There is no current event loop in thread 'MainThread'.

----------------------------------------------------------------------
Ran 2 tests in 0.001s

What am I missing?

--
Pradip Caulagi
http://caulagi.com