docstr: Test to verify the exit mechanism of airflow-worker cli
  by mocking validate_session method
docstr_tok: ["Test","to","verify","the","exit","mechanism","of","airflow-worker","cli","by","mocking","validate_session","method"]
code: def test_error(self, mock_validate_session):
      """
      Test to verify the exit mechanism of airflow-worker cli
      by mocking validate_session method
      """
      mock_validate_session.return_value = False
      with pytest.raises(SystemExit) as ctx, conf_vars(
          {("core", "executor"): "CeleryExecutor"}
      ):
          celery_command.worker(Namespace(queues=1, concurrency=1))
      assert (
          str(ctx.value)
          == "Worker exiting, database connection precheck failed."
      )
  
imports: from __future__ import annotations
  import importlib
  import os
  from argparse import Namespace
  from unittest import mock
  import pytest
  import sqlalchemy
  import airflow
  from airflow.cli import cli_parser
  from airflow.cli.commands import celery_command
  from airflow.configuration import conf
  from tests.test_utils.config import conf_vars
label_desc: Use image node_id 1 for calling the TestWorkerPrecheck obj's underlying member method code with example usage: obj.test_error(mock_validate_session) without return types