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Pytest support for asyncio.

Project description

pytest-asyncio is an Apache2 licensed library, written in Python, for testing asyncio code with pytest.

asyncio code is usually written in the form of coroutines, which makes it slightly more difficult to test using normal testing tools. pytest-asyncio provides useful fixtures and markers to make testing easier.

def test_some_asyncio_code():
    res = yield from library.do_something()
    assert b'expected result' == res

pytest-asyncio has been strongly influenced by pytest-tornado.


  • fixtures for creating and injecting versions of the asyncio event loop

  • fixtures for injecting unused tcp ports

  • pytest markers for treating tests as asyncio coroutines


To install pytest-asyncio, simply:

$ pip install pytest-asyncio

This is enough for pytest to pick up pytest-asyncio.



Creates and injects a new instance of the default asyncio event loop. The loop will be closed at the end of the test.

Note that just using the event_loop fixture won’t make your test function a coroutine. You’ll need to interact with the event loop directly, using methods like event_loop.run_until_complete. See the pytest.mark.asyncio marker for treating test functions like coroutines.

def test_http_client(event_loop):
    url = ''
    resp = event_loop.run_until_complete(http_client(url))
    assert b'HTTP/1.1 200 OK' in resp


The event_loop_process_pool fixture is almost identical to the event_loop fixture, except the created event loop will have a concurrent.futures.ProcessPoolExecutor set as the default executor.


Finds and yields a single unused TCP port on the localhost interface. Useful for binding temporary test servers.


A callable which returns a different unused TCP port each invocation. Useful when several unused TCP ports are required in a test.

def a_test(unused_tcp_port_factory):
    port1, port2 = unused_tcp_port_factory(), unused_tcp_port_factory()



Mark your test coroutine with this marker and pytest will execute it as an asyncio task using the event loop provided by the event_loop fixture. See the introductory section for an example.


The asyncio_process_pool marker is almost identical to the asyncio marker, except the event loop used will have a concurrent.futures.ProcessPoolExecutor set as the default executor.


Contributions are very welcome. Tests can be run with tox, please ensure the coverage at least stays the same before you submit a pull request.

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