def METHOD_NAME(
    mock_bq_client: mock.MagicMock,
    mock_split_county: mock.MagicMock,
    client: FlaskClient
):
    # Set up mocks
    mock_bq_instance = mock_bq_client.return_value
    mock_bq_instance.list_tables.return_value = TEST_TABLES
    payload = {
        'dataset_name': 'my-dataset',
        'demographic': 'age'
    }
    response = client.post('/', json=payload)
    assert response.status_code == 204
    # called once per "age" table
    assert mock_bq_instance.extract_table.call_count == 3
    # called once per "age" table, only continues for county level files
    assert mock_split_county.call_count == 3