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py.test plugin for testing Python 3.5+ Tornado code

Project description

A simple pytest plugin that provides some helpful fixtures for testing Tornado (version 5.0 or newer) apps and easy handling of plain (undecoratored) native coroutine tests (Python 3.5+).

Why another Tornado pytest plugin when the excellent pytest-tornado already exists? The main reason is that I didn’t want to have to decorate every test coroutine with @pytest.mark.gen_test. This plugin doesn’t have anything like gen_test. Defining a test with async def and a name that begins with test_ is all that is required.


Install using pip, which must be run with Python 3.5+:

pip install pytest-tornasync


Define an app fixture:

import pytest

def app():
    import yourapp
    return yourapp.make_app()  # a tornado.web.Application

Create tests as native coroutines using Python 3.5+ async def:

async def test_app(http_server_client):
    resp = await http_server_client.fetch('/')
    assert resp.code == 200
    # ...


When the plugin is installed, then pytest --fixtures will show the fixtures that are available:


Port used by http_server.


Start a tornado HTTP server that listens on all available interfaces.

You must create an app fixture, which returns the tornado.web.Application to be tested.

Raises: FixtureLookupError: tornado application fixture not found


Create an asynchronous HTTP client that can fetch from http_server.


Create an asynchronous HTTP client that can fetch from anywhere.


Create a new tornado.ioloop.IOLoop for each test case.


import time

import tornado.web
import tornado.gen

import pytest

class MainHandler(tornado.web.RequestHandler):
    def get(self):
        self.write("Hello, world!")

def app():
    return tornado.web.Application([(r"/", MainHandler)])

async def test_http_server_client(http_server_client):
    # http_server_client fetches from the `app` fixture and takes path
    resp = await http_server_client.fetch('/')
    assert resp.code == 200
    assert resp.body == b"Hello, world!"

async def test_http_client(http_client):
    # http_client fetches from anywhere and takes full URL
    resp = await http_client.fetch('')
    assert resp.code == 204

async def example_coroutine(period):
    await tornado.gen.sleep(period)

async def test_example():
    # no fixtures needed
    period = 1.0
    start = time.time()
    await example_coroutine(period)
    elapsed = time.time() - start
    assert elapsed >= period


0.6.0 (2018-11-19)

  • minor updates to avoid a pytest warning under pytest 4

  • repo switch to using a ‘src’ dir

0.5.0 (2018-05-28)

  • updated to work with Tornado 5, which is now the minimum required version

  • require pytest >= 3.0

  • the io_loop fixture always refers to a tornado.ioloop.IOLoop instance now

  • the io_loop_asyncio and io_loop_tornado fixtures have been removed, since now that Tornado 5 always uses asyncio under Python 3, there would be no difference between the two fixtures, so io_loop is all that is needed

  • tox tests now test more versions of Tornado (5.0.* and latest 5.*), Pytest (3.0.* and latest 3.*), and Python (3.5, 3.6, 3.7, and pypy3).

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