pytest-tornado

library0.8.1pypypi✓ verified 89d ago

pytest-tornado is a plugin for the Pytest testing framework that simplifies testing asynchronous Tornado applications. It provides a set of fixtures and markers designed to integrate Tornado's asynchronous features seamlessly into pytest tests. The current version is 0.8.1, released on June 17, 2020, and the project has an infrequent release cadence.

testing

pip install pytest-tornado

github ↗package ↗

INSTALL

IMPORT

SIG · PYTEST-TORNADO

pytest-tornado

testingpythonv0.8.1

Install

3.2s avg

Import

424ms

Disk

37MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v0.8.1 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.920 runs

installs and imports cleanly · install 0.0s · import 0.444s · 34.2MB

glibc

py 3.10–3.920 runs

installs and imports cleanly · install 3.2s · import 0.405s · 35MB

37MB installed

● package 37MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

pytest.mark.gen_test

✓ import pytest

Used as a decorator for Tornado coroutine tests. No direct imports from `pytest_tornado` are typically needed as it provides fixtures.

This quickstart demonstrates how to test a simple Tornado web application using `pytest-tornado`. It defines a Tornado application, provides it via a `pytest` fixture named `app`, and then uses the `@pytest.mark.gen_test` marker along with `http_client` and `base_url` fixtures to perform an asynchronous HTTP request and assert the response.

import pytest import tornado.web import tornado.httpclient class MainHandler(tornado.web.RequestHandler): def get(self): self.write("Hello, world") application = tornado.web.Application([ (r"/", MainHandler), ]) @pytest.fixture def app(): return application @pytest.mark.gen_test async def test_hello_world(http_client, base_url): response = await http_client.fetch(base_url) assert response.code == 200 assert response.body == b"Hello, world" # To run: `pytest your_test_file.py`

Debug

Known issues

gotchaWhen testing native `async def` coroutines (Python 3.5+, Tornado 5.0+), the `@pytest.mark.gen_test` decorator, which is designed for `tornado.gen.coroutine` style, might feel less intuitive. While it can still be used, alternatives like `pytest-tornasync` offer direct support for `async def` without this decorator.

fix

For native `async def` tests, consider `pytest-tornasync` or ensure `@pytest.mark.gen_test` is correctly applied. For complex scenarios, you might need to combine it with `pytest-asyncio` (see next warning).

affects: All versions with Tornado >= 5.0

gotchaCombining `pytest-tornado` with `pytest-asyncio` can lead to issues if decorators are incorrectly ordered or event loops are mismanaged. The `asyncio` event loop might not run, causing tests to hang or fail with `RuntimeError: no current event loop in thread`.

fix

If using both, ensure the `@pytest.mark.asyncio` decorator, if needed to manage the event loop, wraps `@pytest.mark.gen_test` for the `asyncio` loop to be properly initiated. Alternatively, streamline your setup to primarily use one async plugin if possible, or ensure explicit `IOLoop` management if mixing concerns.

affects: All versions when used with `pytest-asyncio`

gotchaTests can hang indefinitely if a Tornado `IOLoop` instance, especially one running in a separate thread or manually managed, is not explicitly shut down after test completion. `pytest-tornado` fixtures (`io_loop`, `http_server`) typically handle this automatically for tests using them.

fix

Ensure any manually created `IOLoop` instances are properly stopped (e.g., `io_loop.stop()`, `io_loop.close()`) in test teardown or fixture finalizers. If the `IOLoop` is in another thread, ensure you stop the *correct* `IOLoop` instance from that thread.

affects: All versions, particularly with custom `IOLoop` management

Errors

Common errors & fixes

pytest hangs after tests complete

The Tornado IOLoop, especially one manually managed or running in a separate thread for a test server, was not properly shut down, preventing pytest from exiting.

fix

Ensure that any custom `tornado.ioloop.IOLoop` instances are explicitly stopped using `io_loop.stop()` and `io_loop.close()`. If the IOLoop is in a separate thread, make sure you are stopping the instance created and running within that specific thread. pytest-tornado's provided fixtures (e.g., `http_server`) should handle their IOLoop lifecycle automatically.

RuntimeError: no current event loop in thread (or similar 'Future waiting for an event loop to be running')

This error arises when `async def` functions or `asyncio`-based code is executed in a test without an active `asyncio` event loop. This often happens when mixing `pytest-tornado`'s `@pytest.mark.gen_test` with `pytest-asyncio` or native `async/await` without proper event loop management.

fix

If using `pytest-asyncio`, ensure its decorator (`@pytest.mark.asyncio`) is placed *outside* or manages the context for `@pytest.mark.gen_test` if both are applied. For simple native coroutine tests with Tornado 5.0+, consider if `pytest-tornasync` is a better fit as it handles `async def` more directly.

Deadlock or tests hanging when using external browser automation (e.g., Splinter, Selenium)

External, blocking browser drivers run synchronously and can contend with the asynchronous `IOLoop` that the Tornado application is running on within the same test context, preventing the server from processing requests.

fix

Run the Tornado application in a separate thread or process that is distinct from the main test `IOLoop` where the blocking browser automation operates. This allows the server to respond independently of the blocking client.

Upgrade

Version history

0.8.1latest on PyPI · released Jun 17, 2020

Audit

Dependencies

pytestrequiredCore testing framework

tornadorequiredAsynchronous web framework

setuptoolsrequiredBuild and distribution utility

Agent activity

7 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/eugeniy/pytest-tornado ↗

packagehttps://pypi.org/project/pytest-tornado/ ↗