test.py

#!/usr/bin/env python3

from requests import post
from flask import Flask, request
from threading import Thread
from os import urandom
from io import BytesIO
import time

SIZE = 3000 # Size in bytes

app = Flask(__name__)
app.debug = True

destination = BytesIO()

@app.post("/")
def upload_file():
    print("Got Pinged")
    if "file" not in request.files:
        return '', 400

    file = request.files["file"]
    file.save(destination)
    return ''

thread = Thread(target=app.run, kwargs={"use_reloader": False, "port": 8880})
thread.daemon = True
thread.start()

content = urandom(SIZE)
file = BytesIO(content)

response = post("http://localhost:8880/", files={
         "file": file
     })

assert response.status_code == 200, f"Expected 200 OK, got {response.status_code}"

assert content == destination.getvalue()