test_app.py

import sys
import os
import requests
import time
import subprocess

sys.path.append(os.getcwd())

proc = subprocess.Popen([".venv/bin/python", "app.py"], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
time.sleep(25)
if proc.poll() is not None:
    print("App crashed!")
    out, err = proc.communicate()
    print(err.decode())
else:
    print("App running successfully.")
    proc.kill()