使用 PyTest 进行测试时如何在后台启动 Uvicorn + FastAPI

Question

我有一个用Uvicorn + FastAPI编写的 REST-API 应用程序

我想使用 PyTest 进行测试。

我想在开始测试时在夹具中启动服务器，因此当测试完成时，夹具将终止应用程序。

FastAPI 测试展示了如何测试 API 应用程序，

from fastapi import FastAPI
from starlette.testclient import TestClient

app = FastAPI()


@app.get("/")
async def read_main():
    return {"msg": "Hello World"}


client = TestClient(app)


def test_read_main():
    response = client.get("/")
    assert response.status_code == 200
    assert response.json() == {"msg": "Hello World"}

这不会以通常的方式使服务器联机。似乎由 client.get 命令触发的特定功能是唯一运行的东西。

我找到了这些额外的资源，但我无法让它们为我工作：

https://medium.com/@hmajid2301/pytest-with-background-thread-fixtures-f0dc34ee3c46

如何将服务器作为 py.test 的夹具运行

您将如何从 PyTest 运行 Uvicorn+FastAPI 应用程序，以便它随着测试而上升和下降？

Answer 1

灵感来自@Gabriel C 答案。完全面向对象的异步方法（使用出色的 asynctest 框架）。

import logging
from fastapi import FastAPI

class App:
    """ Core application to test. """

    def __init__(self):
        self.api = FastAPI()
        # register endpoints
        self.api.get("/")(self.read_root)
        self.api.on_event("shutdown")(self.close)

    async def close(self):
        """ Gracefull shutdown. """
        logging.warning("Shutting down the app.")

    async def read_root(self):
        """ Read the root. """
        return {"Hello": "World"}

""" Testing part."""
from multiprocessing import Process
import asynctest
import asyncio
import aiohttp
import uvicorn

class TestApp(asynctest.TestCase):
    """ Test the app class. """

    async def setUp(self):
        """ Bring server up. """
        app = App()
        self.proc = Process(target=uvicorn.run,
                            args=(app.api,),
                            kwargs={
                                "host": "127.0.0.1",
                                "port": 5000,
                                "log_level": "info"},
                            daemon=True)
        self.proc.start()
        await asyncio.sleep(0.1)  # time for the server to start

    async def tearDown(self):
        """ Shutdown the app. """
        self.proc.terminate()

    async def test_read_root(self):
        """ Fetch an endpoint from the app. """
        async with aiohttp.ClientSession() as session:
            async with session.get("http://127.0.0.1:5000/") as resp:
                data = await resp.json()
        self.assertEqual(data, {"Hello": "World"})

Answer 2

如果你想启动服务器，你必须在不同的进程/线程中进行，因为 uvicorn.run() 是一个阻塞调用。

然后，您将不得不使用诸如请求之类的东西来访问服务器正在侦听的实际 URL，而不是使用 TestClient。

from multiprocessing import Process

import pytest
import requests
import uvicorn
from fastapi import FastAPI

app = FastAPI()


@app.get("/")
async def read_main():
    return {"msg": "Hello World"}


def run_server():
    uvicorn.run(app)


@pytest.fixture
def server():
    proc = Process(target=run_server, args=(), daemon=True)
    proc.start() 
    yield
    proc.kill() # Cleanup after test


def test_read_main(server):
    response = requests.get("http://localhost:8000/")
    assert response.status_code == 200
    assert response.json() == {"msg": "Hello World"}

Answer 3

这里我有另一个在同一进程中运行 uvicorn 的解决方案（使用 Python 3.7.9 测试）：

from typing import List, Optional
import asyncio

import pytest

import uvicorn

PORT = 8000


class UvicornTestServer(uvicorn.Server):
    """Uvicorn test server

    Usage:
        @pytest.fixture
        server = UvicornTestServer()
        await server.up()
        yield
        await server.down()
    """

    def __init__(self, app, host='127.0.0.1', port=PORT):
        """Create a Uvicorn test server

        Args:
            app (FastAPI, optional): the FastAPI app. Defaults to main.app.
            host (str, optional): the host ip. Defaults to '127.0.0.1'.
            port (int, optional): the port. Defaults to PORT.
        """
        self._startup_done = asyncio.Event()
        super().__init__(config=uvicorn.Config(app, host=host, port=port))

    async def startup(self, sockets: Optional[List] = None) -> None:
        """Override uvicorn startup"""
        await super().startup(sockets=sockets)
        self.config.setup_event_loop()
        self._startup_done.set()

    async def up(self) -> None:
        """Start up server asynchronously"""
        self._serve_task = asyncio.create_task(self.serve())
        await self._startup_done.wait()

    async def down(self) -> None:
        """Shut down server asynchronously"""
        self.should_exit = True
        await self._serve_task


@pytest.fixture
async def startup_and_shutdown_server():
    """Start server as test fixture and tear down after test"""
    server = UvicornTestServer()
    await server.up()
    yield
    await server.down()


@pytest.mark.asyncio
async def test_chat_simple(startup_and_shutdown_server):
    """A simple websocket test"""
    # any test code here