1pytest-asyncio: pytest support for asyncio 2========================================== 3 4.. image:: https://img.shields.io/pypi/v/pytest-asyncio.svg 5 :target: https://pypi.python.org/pypi/pytest-asyncio 6.. image:: https://travis-ci.org/pytest-dev/pytest-asyncio.svg?branch=master 7 :target: https://travis-ci.org/pytest-dev/pytest-asyncio 8.. image:: https://coveralls.io/repos/pytest-dev/pytest-asyncio/badge.svg 9 :target: https://coveralls.io/r/pytest-dev/pytest-asyncio 10.. image:: https://img.shields.io/pypi/pyversions/pytest-asyncio.svg 11 :target: https://github.com/pytest-dev/pytest-asyncio 12 :alt: Supported Python versions 13 14pytest-asyncio is an Apache2 licensed library, written in Python, for testing 15asyncio code with pytest. 16 17asyncio code is usually written in the form of coroutines, which makes it 18slightly more difficult to test using normal testing tools. pytest-asyncio 19provides useful fixtures and markers to make testing easier. 20 21.. code-block:: python 22 23 @pytest.mark.asyncio 24 async def test_some_asyncio_code(): 25 res = await library.do_something() 26 assert b'expected result' == res 27 28pytest-asyncio has been strongly influenced by pytest-tornado_. 29 30.. _pytest-tornado: https://github.com/eugeniy/pytest-tornado 31 32Features 33-------- 34 35- fixtures for creating and injecting versions of the asyncio event loop 36- fixtures for injecting unused tcp ports 37- pytest markers for treating tests as asyncio coroutines 38- easy testing with non-default event loops 39- support for `async def` fixtures and async generator fixtures 40 41Installation 42------------ 43 44To install pytest-asyncio, simply: 45 46.. code-block:: bash 47 48 $ pip install pytest-asyncio 49 50This is enough for pytest to pick up pytest-asyncio. 51 52Fixtures 53-------- 54 55``event_loop`` 56~~~~~~~~~~~~~~ 57Creates and injects a new instance of the default asyncio event loop. By 58default, the loop will be closed at the end of the test (i.e. the default 59fixture scope is ``function``). 60 61Note that just using the ``event_loop`` fixture won't make your test function 62a coroutine. You'll need to interact with the event loop directly, using methods 63like ``event_loop.run_until_complete``. See the ``pytest.mark.asyncio`` marker 64for treating test functions like coroutines. 65 66Simply using this fixture will not set the generated event loop as the 67default asyncio event loop, or change the asyncio event loop policy in any way. 68Use ``pytest.mark.asyncio`` for this purpose. 69 70.. code-block:: python 71 72 def test_http_client(event_loop): 73 url = 'http://httpbin.org/get' 74 resp = event_loop.run_until_complete(http_client(url)) 75 assert b'HTTP/1.1 200 OK' in resp 76 77This fixture can be easily overridden in any of the standard pytest locations 78(e.g. directly in the test file, or in ``conftest.py``) to use a non-default 79event loop. This will take effect even if you're using the 80``pytest.mark.asyncio`` marker and not the ``event_loop`` fixture directly. 81 82.. code-block:: python 83 84 @pytest.fixture 85 def event_loop(): 86 loop = MyCustomLoop() 87 yield loop 88 loop.close() 89 90If the ``pytest.mark.asyncio`` marker is applied, a pytest hook will 91ensure the produced loop is set as the default global loop. 92Fixtures depending on the ``event_loop`` fixture can expect the policy to be properly modified when they run. 93 94``unused_tcp_port`` 95~~~~~~~~~~~~~~~~~~~ 96Finds and yields a single unused TCP port on the localhost interface. Useful for 97binding temporary test servers. 98 99``unused_tcp_port_factory`` 100~~~~~~~~~~~~~~~~~~~~~~~~~~~ 101A callable which returns a different unused TCP port each invocation. Useful 102when several unused TCP ports are required in a test. 103 104.. code-block:: python 105 106 def a_test(unused_tcp_port_factory): 107 port1, port2 = unused_tcp_port_factory(), unused_tcp_port_factory() 108 ... 109 110Async fixtures 111~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 112Asynchronous fixtures are defined just like ordinary pytest fixtures, except they should be coroutines or asynchronous generators. 113 114.. code-block:: python3 115 116 @pytest.fixture 117 async def async_gen_fixture(): 118 await asyncio.sleep(0.1) 119 yield 'a value' 120 121 @pytest.fixture(scope='module') 122 async def async_fixture(): 123 return await asyncio.sleep(0.1) 124 125All scopes are supported, but if you use a non-function scope you will need 126to redefine the ``event_loop`` fixture to have the same or broader scope. 127Async fixtures need the event loop, and so must have the same or narrower scope 128than the ``event_loop`` fixture. 129 130If you want to do this with Python 3.5, the ``yield`` statement must be replaced with ``await yield_()`` and the coroutine 131function must be decorated with ``@async_generator``, like so: 132 133.. code-block:: python3 134 135 from async_generator import yield_, async_generator 136 137 @pytest.fixture 138 @async_generator 139 async def async_gen_fixture(): 140 await asyncio.sleep(0.1) 141 await yield_('a value') 142 143 144Markers 145------- 146 147``pytest.mark.asyncio`` 148~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 149Mark your test coroutine with this marker and pytest will execute it as an 150asyncio task using the event loop provided by the ``event_loop`` fixture. See 151the introductory section for an example. 152 153The event loop used can be overriden by overriding the ``event_loop`` fixture 154(see above). 155 156In order to make your test code a little more concise, the pytest |pytestmark|_ 157feature can be used to mark entire modules or classes with this marker. 158Only test coroutines will be affected (by default, coroutines prefixed by 159``test_``), so, for example, fixtures are safe to define. 160 161.. code-block:: python 162 163 import asyncio 164 import pytest 165 166 # All test coroutines will be treated as marked. 167 pytestmark = pytest.mark.asyncio 168 169 async def test_example(event_loop): 170 """No marker!""" 171 await asyncio.sleep(0, loop=event_loop) 172 173.. |pytestmark| replace:: ``pytestmark`` 174.. _pytestmark: http://doc.pytest.org/en/latest/example/markers.html#marking-whole-classes-or-modules 175 176Changelog 177--------- 1780.13.0 (2020-06-24) 179~~~~~~~~~~~~~~~~~~~ 180- Fix `#162 <https://github.com/pytest-dev/pytest-asyncio/issues/162>`_, and ``event_loop`` fixture behavior now is coherent on all scopes. 181 `#164 <https://github.com/pytest-dev/pytest-asyncio/pull/164>`_ 182 1830.12.0 (2020-05-04) 184~~~~~~~~~~~~~~~~~~~ 185- Run the event loop fixture as soon as possible. This helps with fixtures that have an implicit dependency on the event loop. 186 `#156 <https://github.com/pytest-dev/pytest-asyncio/pull/156>`_ 187 1880.11.0 (2020-04-20) 189~~~~~~~~~~~~~~~~~~~ 190- Test on 3.8, drop 3.3 and 3.4. Stick to 0.10 for these versions. 191 `#152 <https://github.com/pytest-dev/pytest-asyncio/pull/152>`_ 192- Use the new Pytest 5.4.0 Function API. We therefore depend on pytest >= 5.4.0. 193 `#142 <https://github.com/pytest-dev/pytest-asyncio/pull/142>`_ 194- Better ``pytest.skip`` support. 195 `#126 <https://github.com/pytest-dev/pytest-asyncio/pull/126>`_ 196 1970.10.0 (2019-01-08) 198~~~~~~~~~~~~~~~~~~~~ 199- ``pytest-asyncio`` integrates with `Hypothesis <https://hypothesis.readthedocs.io>`_ 200 to support ``@given`` on async test functions using ``asyncio``. 201 `#102 <https://github.com/pytest-dev/pytest-asyncio/pull/102>`_ 202- Pytest 4.1 support. 203 `#105 <https://github.com/pytest-dev/pytest-asyncio/pull/105>`_ 204 2050.9.0 (2018-07-28) 206~~~~~~~~~~~~~~~~~~ 207- Python 3.7 support. 208- Remove ``event_loop_process_pool`` fixture and 209 ``pytest.mark.asyncio_process_pool`` marker (see 210 https://bugs.python.org/issue34075 for deprecation and removal details) 211 2120.8.0 (2017-09-23) 213~~~~~~~~~~~~~~~~~~ 214- Improve integration with other packages (like aiohttp) with more careful event loop handling. 215 `#64 <https://github.com/pytest-dev/pytest-asyncio/pull/64>`_ 216 2170.7.0 (2017-09-08) 218~~~~~~~~~~~~~~~~~~ 219- Python versions pre-3.6 can use the async_generator library for async fixtures. 220 `#62 <https://github.com/pytest-dev/pytest-asyncio/pull/62>` 221 222 2230.6.0 (2017-05-28) 224~~~~~~~~~~~~~~~~~~ 225- Support for Python versions pre-3.5 has been dropped. 226- ``pytestmark`` now works on both module and class level. 227- The ``forbid_global_loop`` parameter has been removed. 228- Support for async and async gen fixtures has been added. 229 `#45 <https://github.com/pytest-dev/pytest-asyncio/pull/45>`_ 230- The deprecation warning regarding ``asyncio.async()`` has been fixed. 231 `#51 <https://github.com/pytest-dev/pytest-asyncio/pull/51>`_ 232 2330.5.0 (2016-09-07) 234~~~~~~~~~~~~~~~~~~ 235- Introduced a changelog. 236 `#31 <https://github.com/pytest-dev/pytest-asyncio/issues/31>`_ 237- The ``event_loop`` fixture is again responsible for closing itself. 238 This makes the fixture slightly harder to correctly override, but enables 239 other fixtures to depend on it correctly. 240 `#30 <https://github.com/pytest-dev/pytest-asyncio/issues/30>`_ 241- Deal with the event loop policy by wrapping a special pytest hook, 242 ``pytest_fixture_setup``. This allows setting the policy before fixtures 243 dependent on the ``event_loop`` fixture run, thus allowing them to take 244 advantage of the ``forbid_global_loop`` parameter. As a consequence of this, 245 we now depend on pytest 3.0. 246 `#29 <https://github.com/pytest-dev/pytest-asyncio/issues/29>`_ 247 248 2490.4.1 (2016-06-01) 250~~~~~~~~~~~~~~~~~~ 251- Fix a bug preventing the propagation of exceptions from the plugin. 252 `#25 <https://github.com/pytest-dev/pytest-asyncio/issues/25>`_ 253 2540.4.0 (2016-05-30) 255~~~~~~~~~~~~~~~~~~ 256- Make ``event_loop`` fixtures simpler to override by closing them in the 257 plugin, instead of directly in the fixture. 258 `#21 <https://github.com/pytest-dev/pytest-asyncio/pull/21>`_ 259- Introduce the ``forbid_global_loop`` parameter. 260 `#21 <https://github.com/pytest-dev/pytest-asyncio/pull/21>`_ 261 2620.3.0 (2015-12-19) 263~~~~~~~~~~~~~~~~~~ 264- Support for Python 3.5 ``async``/``await`` syntax. 265 `#17 <https://github.com/pytest-dev/pytest-asyncio/pull/17>`_ 266 2670.2.0 (2015-08-01) 268~~~~~~~~~~~~~~~~~~ 269- ``unused_tcp_port_factory`` fixture. 270 `#10 <https://github.com/pytest-dev/pytest-asyncio/issues/10>`_ 271 272 2730.1.1 (2015-04-23) 274~~~~~~~~~~~~~~~~~~ 275Initial release. 276 277 278Contributing 279------------ 280Contributions are very welcome. Tests can be run with ``tox``, please ensure 281the coverage at least stays the same before you submit a pull request. 282