def METHOD_NAME(mock_os_fork):
    mock_os_fork.return_value = 0
    arbiter = gunicorn.arbiter.Arbiter(DummyApplication())
    arbiter.cfg.settings['worker_exit'] = mock.Mock()
    arbiter.pid = None
    mock_worker = mock.Mock()
    arbiter.worker_class = mock.Mock(return_value=mock_worker)
    try:
        arbiter.spawn_worker()
    except SystemExit:
        pass
    arbiter.cfg.worker_exit.assert_called_with(arbiter, mock_worker)