As discussed in  https://github.com/apache/airflow/pull/15534#discussion_r620500075, we could possibly rewrite Beam Hook to remove the need of storing state in it.
self, mock_run, mock_get_conn, mock_provide_authorized_gcloud, mock_controller
    ):
        test_job = {"id": "TEST_JOB_ID"}
        mock_controller.return_value.get_jobs.return_value = [test_job]
        mock_run.return_value = mock.MagicMock(
            stdout=f"{TEST_JOB_ID}\n".encode(), stderr=f"{TEST_JOB_ID}\n".encode(), returncode=0
        )
        on_new_job_callback = mock.MagicMock()
        result = self.dataflow_hook.start_sql_job(
            job_name=TEST_SQL_JOB_NAME,
            query=TEST_SQL_QUERY,
            options=TEST_SQL_OPTIONS,
            location=TEST_LOCATION,
            project_id=TEST_PROJECT,
            on_new_job_callback=on_new_job_callback,
        )
        mock_run.assert_called_once_with(
            [
                "gcloud",
                "dataflow",