code: def test_cli_webserver_background(self, tmp_path):
      with mock.patch.dict(
          "os.environ",
          AIRFLOW__CORE__DAGS_FOLDER="/dev/null",
          AIRFLOW__CORE__LOAD_EXAMPLES="False",
          AIRFLOW__WEBSERVER__WORKERS="1",
      ):
          pidfile_webserver = tmp_path / "pidflow-webserver.pid"
          pidfile_monitor = tmp_path / "pidflow-webserver-monitor.pid"
          stdout = tmp_path / "airflow-webserver.out"
          stderr = tmp_path / "airflow-webserver.err"
          logfile = tmp_path / "airflow-webserver.log"
          try:
              # Run webserver as daemon in background. Note that the wait method is not called.
  
              proc = subprocess.Popen(
                  [
                      "airflow",
                      "webserver",
                      "--daemon",
                      "--pid",
                      os.fspath(pidfile_webserver),
                      "--stdout",
                      os.fspath(stdout),
                      "--stderr",
                      os.fspath(stderr),
                      "--log-file",
                      os.fspath(logfile),
                  ]
              )
              assert proc.poll() is None
  
              pid_monitor = self._wait_pidfile(pidfile_monitor)
              console.print(f"[blue]Monitor started at {pid_monitor}")
              pid_webserver = self._wait_pidfile(pidfile_webserver)
              console.print(
                  f"[blue]Webserver started at {pid_webserver}"
              )
              console.print("[blue]Running airflow webserver process:")
              # Assert that the webserver and gunicorn processes are running (by name rather than pid).
              assert self._find_process(
                  r"airflow webserver", print_found_process=True
              )
              console.print("[blue]Waiting for gunicorn processes:")
              # wait for gunicorn to start
              for i in range(30):
                  if self._find_process(r"^gunicorn"):
                      break
                  console.print(
                      "[blue]Waiting for gunicorn to start ..."
                  )
                  time.sleep(1)
              console.print("[blue]Running gunicorn processes:")
              assert self._find_all_processes(
                  "^gunicorn", print_found_process=True
              )
              console.print(
                  "[magenta]Webserver process started successfully."
              )
              console.print(
                  "[magenta]Terminating monitor process and expect "
                  "Webserver and gunicorn processes to terminate as well"
              )
              proc = psutil.Process(pid_monitor)
              proc.terminate()
              assert proc.wait(120) in (0, None)
              self._check_processes(ignore_running=False)
              console.print(
                  "[magenta]All Webserver and gunicorn processes are terminated."
              )
          except Exception:
              console.print(
                  "[red]Exception occurred. Dumping all logs."
              )
              # Dump all logs
              for file in tmp_path.glob("*"):
                  console.print(
                      f"Dumping {file} (size: {file.stat().st_size})"
                  )
                  console.print(file.read_text())
              raise
  
imports: from __future__ import annotations
  import os
  import subprocess
  import sys
  import time
  from unittest import mock
  import psutil
  import pytest
  from rich.console import Console
  from airflow import settings
  from airflow.cli import cli_parser
  from airflow.cli.commands import webserver_command
  from airflow.cli.commands.webserver_command import GunicornMonitor
  from tests.cli.commands._common_cli_classes import _ComonCLIGunicornTestClass
  from tests.test_utils.config import conf_vars
label_desc: Use image node_id 1 for calling the TestCliWebServer obj's underlying member method code with example usage: obj.test_cli_webserver_background(tmp_path) without return types