pytest-twisted - test twisted code with pytest

Authors:	Ralf Schmitt, Kyle Altendorf, Victor Titor
Version:	1.7.1
Date:	2018-03-08
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.

Installation

Install the plugin with:

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.

Presently only qt5reactor is supported for use with pyqt5 and pytest-qt. 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.

Beware that in situations such as a conftest.py file that the name pytest_twisted may be undesirably detected by pytest as an unknown hook. One alternative is to import pytest_twisted as pt.

inlineCallbacks

Using twisted.internet.defer.inlineCallbacks as a decorator for test functions, which take funcargs, 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 == []

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)

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 funcarg. 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 all.