pytest-asyncio: pytest support for asyncio
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.
@pytest.mark.asyncio async def test_some_asyncio_code(): res = await 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
- easy testing with non-default event loops
- support for async def fixtures and async generator fixtures
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. By
default, the loop will be closed at the end of the test (i.e. the default
fixture scope is
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
event_loop.run_until_complete. See the
for treating test functions like coroutines.
Simply using this fixture will not set the generated event loop as the
default asyncio event loop, or change the asyncio event loop policy in any way.
pytest.mark.asyncio for this purpose.
def test_http_client(event_loop): url = 'http://httpbin.org/get' resp = event_loop.run_until_complete(http_client(url)) assert b'HTTP/1.1 200 OK' in resp
This fixture can be easily overridden in any of the standard pytest locations
(e.g. directly in the test file, or in
conftest.py) to use a non-default
event loop. This will take effect even if you're using the
pytest.mark.asyncio marker and not the
event_loop fixture directly.
@pytest.yield_fixture() def event_loop(): loop = MyCustomLoop() yield loop loop.close()
pytest.mark.asyncio marker is applied, a pytest hook will
ensure the produced loop is set as the default global loop.
Fixtures depending on the
event_loop fixture can expect the policy to be properly modified when they run.
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() ...
Asynchronous fixtures are defined just like ordinary pytest fixtures, except they should be coroutines or asynchronous generators.
@pytest.fixture async def async_gen_fixture(): await asyncio.sleep(0.1) yield 'a value' @pytest.fixture(scope='module') async def async_fixture(): return await asyncio.sleep(0.1)
All scopes are supported, but if you use a non-function scope you will need
to redefine the
event_loop fixture to have the same or broader scope.
Async fixtures need the event loop, and so must have the same or narrower scope
If you want to do this with Python 3.5, the
yield statement must be replaced with
await yield_() and the coroutine
function must be decorated with
@async_generator, like so:
from async_generator import yield_, async_generator @pytest.fixture @async_generator async def async_gen_fixture(): await asyncio.sleep(0.1) await yield_('a value')
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 event loop used can be overriden by overriding the
In order to make your test code a little more concise, the pytest
feature can be used to mark entire modules or classes with this marker.
Only test coroutines will be affected (by default, coroutines prefixed by
test_), so, for example, fixtures are safe to define.
import asyncio import pytest # All test coroutines will be treated as marked. pytestmark = pytest.mark.asyncio async def test_example(event_loop): """No marker!""" await asyncio.sleep(0, loop=event_loop)
- Python 3.7 support.
pytest.mark.asyncio_process_poolmarker (see https://bugs.python.org/issue34075 for deprecation and removal details)
- Improve integration with other packages (like aiohttp) with more careful event loop handling. #64 <https://github.com/pytest-dev/pytest-asyncio/pull/64>
- Python versions pre-3.6 can use the async_generator library for async fixtures. #62 <https://github.com/pytest-dev/pytest-asyncio/pull/62>
- Support for Python versions pre-3.5 has been dropped.
pytestmarknow works on both module and class level.
forbid_global_loopparameter has been removed.
- Support for async and async gen fixtures has been added. #45
- The deprecation warning regarding
asyncio.async()has been fixed. #51
- Introduced a changelog. #31
event_loopfixture is again responsible for closing itself. This makes the fixture slightly harder to correctly override, but enables other fixtures to depend on it correctly. #30
- Deal with the event loop policy by wrapping a special pytest hook,
pytest_fixture_setup. This allows setting the policy before fixtures dependent on the
event_loopfixture run, thus allowing them to take advantage of the
forbid_global_loopparameter. As a consequence of this, we now depend on pytest 3.0. #29
- Fix a bug preventing the propagation of exceptions from the plugin. #25
event_loopfixtures simpler to override by closing them in the plugin, instead of directly in the fixture. #21
- Introduce the
- Support for Python 3.5
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.