Using HTTPX for Tornado testing - testing

Question

I'd like to standardize the use of HTTPX for testing regardless of the Python web framework being used. I managed to get it to work with Quart and FastAPI, but I'm having issues with Tornado since it doesn't comply to ASGI, and it uses a particular asynchronous implementation, although it is currently based on asyncio.
The minimal application to test is divided in three parts: main.py, conftest.py and test_hello.py.
app/main.py:
from contextlib import contextmanager
from typing import Iterator
from tornado.httpserver import HTTPServer
from tornado.ioloop import IOLoop
from tornado.web import Application, RequestHandler
from loguru import logger
async def start_resources() -> None:
'''
Initialize resources such as async Redis and Database connections
'''
logger.info('resources started...')
async def close_resources() -> None:
'''
Release resources
'''
logger.info('resources closed...')
class HelloHandler(RequestHandler):
def get(self) -> None:
self.write({'hello': 'world'})
#contextmanager
def create_app() -> Iterator[Application]:
IOLoop.current().run_sync(start_resources)
try:
app = Application([
("/hello", HelloHandler),
])
yield app
finally:
IOLoop.current().run_sync(close_resources)
if __name__ == '__main__':
with create_app() as app:
http_server = HTTPServer(app)
http_server.listen(8000)
logger.info('Listening to port 8000 (use CTRL + C to quit)')
IOLoop.current().start()
tests/conftest.py:
from typing import Iterator, AsyncIterable
from httpx import AsyncClient
from pytest import fixture
from tornado.platform.asyncio import AsyncIOLoop
from tornado.web import Application
from app.main import create_app # isort:skip
#fixture
def app(io_loop: AsyncIOLoop) -> Iterator[Application]:
'''
Return a Tornado.web.Application object with initialized resources
'''
with create_app() as app:
yield app
#fixture
async def client(app: Application,
base_url: str) -> AsyncIterable[AsyncClient]:
async with AsyncClient(base_url=base_url) as _client:
yield _client
tests/test_hello.py:
from httpx import AsyncClient
from pytest import mark
#mark.gen_test
async def test_hello(client: AsyncClient) -> None:
resp = await client.get('/hello')
assert resp.status_code == 200
assert resp.json() == {'hello': 'world'}
And the project structure is this:
.
├── app
│ ├── __init__.py
│ └── main.py
├── poetry.lock
├── pyproject.toml
└── tests
├── conftest.py
├── __init__.py
└── test_hello.py
And the error I get
$ pytest tests/test_hello.py
========================================================================== test session starts ==========================================================================
platform linux -- Python 3.6.9, pytest-5.4.3, py-1.8.2, pluggy-0.13.1
rootdir: /tmp/minimal-app
plugins: tornado-0.8.1
collected 1 item
tests/test_hello.py F [100%]
=============================================================================== FAILURES ================================================================================
______________________________________________________________________________ test_hello _______________________________________________________________________________
client = <async_generator object client at 0x7f78e3de75f8>
#mark.gen_test
async def test_hello(client: AsyncClient) -> None:
> resp = await client.get('/hello')
E AttributeError: 'async_generator' object has no attribute 'get'
tests/test_hello.py:7: AttributeError
------------------------------------------------------------------------- Captured stderr setup -------------------------------------------------------------------------
2020-06-17 10:21:28.574 | INFO | app.main:start_resources:15 - resources started...
----------------------------------------------------------------------- Captured stderr teardown ------------------------------------------------------------------------
2020-06-17 10:21:28.595 | INFO | app.main:close_resources:22 - resources closed...
======================================================================== short test summary info ========================================================================
FAILED tests/test_hello.py::test_hello - AttributeError: 'async_generator' object has no attribute 'get'
=========================================================================== 1 failed in 0.03s ===========================================================================

Answer 1

I could make it work replacing pytest-tornado fixtures for a custom one and adding alt-pytest-asyncio to support asynchronous tests. pytest-tornado is not necessary anymore.
conftest.py:
from typing import AsyncIterable, Iterator
from httpx import AsyncClient
from pytest import fixture
from tornado.httpserver import HTTPServer
from tornado.ioloop import IOLoop
from tornado.platform.asyncio import AsyncIOLoop
from tornado.testing import bind_unused_port
from tornado.web import Application
from app.main import create_app # isort:skip
#fixture
def io_loop() -> AsyncIOLoop:
'''
Copied from https://github.com/eukaryote/pytest-tornasync/blob/master/src/pytest_tornasync/plugin.py#L59-L68
'''
loop = IOLoop()
loop.make_current()
yield loop
loop.clear_current()
loop.close(all_fds=True)
#fixture
def app(io_loop: AsyncIOLoop) -> Iterator[Application]:
'''
Return a Tornado.web.Application object with initialized resources
'''
with create_app() as app:
yield app
#fixture
async def client(app: Application) -> AsyncIterable[AsyncClient]:
'''
Start a HTTPServer each time
'''
http_server = HTTPServer(app)
port = bind_unused_port()[1]
http_server.listen(port)
async with AsyncClient(base_url=f'http://localhost:{port}') as _client:
yield _client
pyproject.toml:
[tool.poetry.dependencies]
python = "^3.8"
tornado = "^6.0.4"
pytest = "^6.0.1"
httpx = "^0.13.3"
loguru = "^0.5.1"
alt-pytest-asyncio = "^0.5.3"
[tool.poetry.dev-dependencies]
[build-system]
requires = ["poetry>=0.12"]
build-backend = "poetry.masonry.api"