Question: I have an application written with Uvicorn + FastAPI. I am testing the response time using PyTest. Referring to How to start a Uvicorn + FastAPI in background when testing with PyTest, I wrote the test. However, I found the application process alive after completing the test when workers >= 2. I want to terminate the application process cleanly at the end of the test. Do you have any idea? The details are as follows. Environment  Windows 10 Bash 4.4.23 (https://cmder.net/) python 3.7.5  Libraries  fastapi == 0.68.0 uvicorn == 0.14.0 requests == 2.26.0 pytest == 6.2.4  Sample Codes  Application: main.py from fastapi import FastAPI app = FastAPI() @app.get("/") def hello_world(): return "hello world"   Test: test_main.py from multiprocessing import Process import pytest import requests import time import uvicorn HOST = "127.0.0.1" PORT = 8765 WORKERS = 1 def run_server(host: str, port: int, workers: int, wait: int = 15) -> Process: proc = Process( target=uvicorn.run, args=("main:app",), kwargs={ "host": host, "port": port, "workers": workers, }, ) proc.start() time.sleep(wait) assert proc.is_alive() return proc def shutdown_server(proc: Process): proc.terminate() for _ in range(5): if proc.is_alive(): time.sleep(5) else: return else: raise Exception("Process still alive") def check_response(host: str, port: int): assert requests.get(f"http://{host}:{port}").text == '"hello world"' def check_response_time(host: str, port: int, tol: float = 1e-2): s = time.time() requests.get(f"http://{host}:{port}") e = time.time() assert e-s < tol @pytest.fixture(scope="session") def server(): proc = run_server(HOST, PORT, WORKERS) try: yield finally: shutdown_server(proc) def test_main(server): check_response(HOST, PORT) check_response_time(HOST, PORT) check_response(HOST, PORT) check_response_time(HOST, PORT)    Execution Result $ curl http://localhost:8765 curl: (7) Failed to connect to localhost port 8765: Connection refused $ pytest test_main.py =============== test session starts =============== platform win32 -- Python 3.7.5, pytest-6.2.4, py-1.10.0, pluggy-0.13.1 rootdir: .\ collected 1 item test_main.py . [100%] =============== 1 passed in 20.23s =============== $ curl http://localhost:8765 curl: (7) Failed to connect to localhost port 8765: Connection refused $ sed -i -e "s/WORKERS = 1/WORKERS = 3/g" test_main.py $ curl http://localhost:8765 curl: (7) Failed to connect to localhost port 8765: Connection refused $ pytest test_main.py =============== test session starts =============== platform win32 -- Python 3.7.5, pytest-6.2.4, py-1.10.0, pluggy-0.13.1 rootdir: .\ collected 1 item test_main.py . [100%] =============== 1 passed in 20.21s =============== $ curl http://localhost:8765 "hello world" $ # Why is localhost:8765 still alive? 

Answer: I have found a solution myself. Thanks > https://stackoverflow.com/a/27034438/16567832 Solution After install psutil by pip install psutil, update test_main.py from multiprocessing import Process import psutil import pytest import requests import time import uvicorn HOST = "127.0.0.1" PORT = 8765 WORKERS = 3 def run_server(host: str, port: int, workers: int, wait: int = 15) -> Process: proc = Process( target=uvicorn.run, args=("main:app",), kwargs={ "host": host, "port": port, "workers": workers, }, ) proc.start() time.sleep(wait) assert proc.is_alive() return proc def shutdown_server(proc: Process): ##### SOLUTION ##### pid = proc.pid parent = psutil.Process(pid) for child in parent.children(recursive=True): child.kill() ##### SOLUTION END #### proc.terminate() for _ in range(5): if proc.is_alive(): time.sleep(5) else: return else: raise Exception("Process still alive") def check_response(host: str, port: int): assert requests.get(f"http://{host}:{port}").text == '"hello world"' def check_response_time(host: str, port: int, tol: float = 1e-2): s = time.time() requests.get(f"http://{host}:{port}") e = time.time() assert e-s < tol @pytest.fixture(scope="session") def server(): proc = run_server(HOST, PORT, WORKERS) try: yield finally: shutdown_server(proc) def test_main(server): check_response(HOST, PORT) check_response_time(HOST, PORT) check_response(HOST, PORT) check_response_time(HOST, PORT)  Execution Result $ curl http://localhost:8765 curl: (7) Failed to connect to localhost port 8765: Connection refused $ pytest test_main.py ================== test session starts ================== platform win32 -- Python 3.7.5, pytest-6.2.4, py-1.10.0, pluggy-0.13.1 rootdir: .\ collected 1 item test_main.py . [100%] ================== 1 passed in 20.24s ================== $ curl http://localhost:8765 curl: (7) Failed to connect to localhost port 8765: Connection refused