nginx-proxy/test/test_server-down/test_no-server-down.py

import pytest

def test_web_has_no_server_down(docker_compose, nginxproxy):
    conf = nginxproxy.get_conf().decode('ASCII')
    r = nginxproxy.get("http://web.nginx-proxy.tld/port")
    assert r.status_code == 200
    assert r.text == "answer from port 81\n"
    assert conf.count("server 127.0.0.1 down;") == 0