pytest-twisted 1.14.3

Description:

pytesttwisted 1.14.3

Authors:
Ralf Schmitt, Kyle Altendorf, Victor Titor

Version:
1.14.3

Date:
2024-08-21

Download:
https://pypi.python.org/pypi/pytest-twisted#downloads

Code:
https://github.com/pytest-dev/pytest-twisted


pytest-twisted is a plugin for pytest, which allows to test code,
which uses the twisted framework. test functions can return Deferred
objects and pytest will wait for their completion with this plugin.

NOTICE: Python 3.8 with asyncio support
In Python 3.8, asyncio changed the default loop implementation to use
their proactor. The proactor does not implement some methods used by
Twisted’s asyncio support. The result is a NotImplementedError
exception such as below.
<snip>
File "c:\projects\pytest-twisted\.tox\py38-asyncioreactor\lib\site-packages\twisted\internet\asyncioreactor.py", line 320, in install
reactor = AsyncioSelectorReactor(eventloop)
File "c:\projects\pytest-twisted\.tox\py38-asyncioreactor\lib\site-packages\twisted\internet\asyncioreactor.py", line 69, in __init__
super().__init__()
File "c:\projects\pytest-twisted\.tox\py38-asyncioreactor\lib\site-packages\twisted\internet\base.py", line 571, in __init__
self.installWaker()
File "c:\projects\pytest-twisted\.tox\py38-asyncioreactor\lib\site-packages\twisted\internet\posixbase.py", line 286, in installWaker
self.addReader(self.waker)
File "c:\projects\pytest-twisted\.tox\py38-asyncioreactor\lib\site-packages\twisted\internet\asyncioreactor.py", line 151, in addReader
self._asyncioEventloop.add_reader(fd, callWithLogger, reader,
File "C:\Python38-x64\Lib\asyncio\events.py", line 501, in add_reader
raise NotImplementedError
NotImplementedError
The previous default, the selector loop, still works but you have to
explicitly set it and do so early. The following conftest.py is provided
for reference.
import sys

import pytest
import pytest_twisted


@pytest.hookimpl(tryfirst=True)
def pytest_configure(config):
# https://twistedmatrix.com/trac/ticket/9766
# https://github.com/pytest-dev/pytest-twisted/issues/80

if (
config.getoption("reactor", "default") == "asyncio"
and sys.platform == 'win32'
and sys.version_info >= (3, 8)
):
import asyncio

selector_policy = asyncio.WindowsSelectorEventLoopPolicy()
asyncio.set_event_loop_policy(selector_policy)


Python 2 support plans
At some point it may become impractical to retain Python 2 support.
Given the small size and very low amount of development it seems
likely that this will not be a near term issue. While I personally
have no need for Python 2 support I try to err on the side of being
helpful so support will not be explicitly removed just to not have to
think about it. If major issues are reported and neither myself nor
the community have time to resolve them then options will be
considered.


Installation
Install the plugin as below.
pip install pytest-twisted


Using the plugin
The plugin is available after installation and can be disabled using
-p no:twisted.
By default twisted.internet.default is used to install the reactor.
This creates the same reactor that import twisted.internet.reactor
would. Alternative reactors can be specified using the --reactor
option. This presently supports qt5reactor for use with pyqt5
and pytest-qt as well as asyncio. This guide describes how to add
support for a new reactor.
The reactor is automatically created prior to the first test but can
be explicitly installed earlier by calling
pytest_twisted.init_default_reactor() or the corresponding function
for the desired alternate reactor.


inlineCallbacks
Using twisted.internet.defer.inlineCallbacks as a decorator for test
functions, which use fixtures, does not work. Please use
pytest_twisted.inlineCallbacks instead.
@pytest_twisted.inlineCallbacks
def test_some_stuff(tmpdir):
res = yield threads.deferToThread(os.listdir, tmpdir.strpath)
assert res == []


ensureDeferred
Using twisted.internet.defer.ensureDeferred as a decorator for test
functions, which use fixtures, does not work. Please use
pytest_twisted.ensureDeferred instead.
@pytest_twisted.ensureDeferred
async def test_some_stuff(tmpdir):
res = await threads.deferToThread(os.listdir, tmpdir.strpath)
assert res == []


Waiting for deferreds in fixtures
pytest_twisted.blockon allows fixtures to wait for deferreds.
@pytest.fixture
def val():
d = defer.Deferred()
reactor.callLater(1.0, d.callback, 10)
return pytest_twisted.blockon(d)


async/await fixtures
async/await fixtures can be used along with yield for normal
pytest fixture semantics of setup, value, and teardown. At present only
function and module scope are supported.
# No yield (coroutine function)
# -> use pytest_twisted.async_fixture()
@pytest_twisted.async_fixture()
async def foo():
d = defer.Deferred()
reactor.callLater(0.01, d.callback, 42)
value = await d
return value

# With yield (asynchronous generator)
# -> use pytest_twisted.async_yield_fixture()
@pytest_twisted.async_yield_fixture()
async def foo_with_teardown():
d1, d2 = defer.Deferred(), defer.Deferred()
reactor.callLater(0.01, d1.callback, 42)
reactor.callLater(0.02, d2.callback, 37)
value = await d1
yield value
await d2


Hypothesis
pytest-twisted can be used with Hypothesis.
@hypothesis.given(x=hypothesis.strategies.integers())
@pytest_twisted.ensureDeferred
async def test_async(x):
assert isinstance(x, int)


The twisted greenlet
Some libraries (e.g. corotwine) need to know the greenlet, which is
running the twisted reactor. It’s available from the
twisted_greenlet fixture. The following code can be used to make
corotwine work with pytest-twisted.
@pytest.fixture(scope="session", autouse=True)
def set_MAIN(request, twisted_greenlet):
from corotwine import protocol
protocol.MAIN = twisted_greenlet
That’s (almost) all.


Deprecations
v1.9

pytest.blockon
Use pytest_twisted.blockon

pytest.inlineCallbacks
Use pytest_twisted.inlineCallbacks