Python 單元測試失敗，因為來自 Mock 的 StopIteration 錯誤

Question

我正在使用 ccxt.binance 模擬測試 class object。 這個模擬的 object 作為參數傳遞給我正在測試的 function。 最初它是有效的，因為我能夠在一定程度上進行測試。 但是，當我更改 object 的值時，function 不遵守該值並返回 StopIteration 錯誤。 我在模擬設置中遺漏了什么嗎？ 這是代碼的示例片段。

這是正在測試的代碼

def exchange_history_load(args, ccxt_exchange):
    # skip exchange if has no true fetchOHLCV or if exchange has no timeframe specific data
    if ((not ccxt_exchange.has['fetchOHLCV']) or (ccxt_exchange.has['fetchOHLCV'] == 'emulated') or
       (not ccxt_exchange.timeframes.get(args.timeframe))):
        logging.warning(f'Skipping {ccxt_exchange.name}.')
        return

    # check if exchange is in database. Write to database if not.
    exchange_db_data = get_exchange(ccxt_exchange.id)
    if not exchange_db_data:
        insert_exchange_to_db(ccxt_exchange.id, ccxt_exchange.name)
        logging.info(f'Inserted {ccxt_exchange.name} to database.')
        exchange_db_data = get_exchange(ccxt_exchange.id)
    exchange_db_id = exchange_db_data[0]
    logging.info(f'Fetched {ccxt_exchange.name} data.')

    # load exchange markets
    markets = ccxt_exchange.load_markets()
    logging.info(f'Loaded {ccxt_exchange.name} markets.')

    return exchange_db_id, markets

這是測試 function

@patch('src.cron.historical_price.hp_load_data.insert_exchange_to_db')
@patch('src.cron.historical_price.hp_load_data.get_exchange')
@patch('ccxt.binance')
def test_exchange_history_load(mock_binance, mock_get_exchange, mock_insert_exchange_to_db):
    # create sample arguments for function
    args = argparse.Namespace(timeframe='1d')

    # mock up sample return values for necessary functions
    mock_get_exchange.side_effect = [None, (1, 'binance', 'Binance'), (1, 'binance', 'Binance')]
    mock_binance.return_value.has.return_value = {'fetchOHLCV': True}
    mock_binance.return_value.load_markets.return_value = {
        'BTC/USDT': {
            'id': 'btcusdt',
            'symbol': 'BTC/USDT',
            'base': 'BTC',
            'quote': 'USDT',
            'active': True
        }
    }
    mock_binance.return_value.id.return_value = 'binance'
    mock_binance.return_value.name.return_value = 'Binance'

    ccxt_exchange = ccxt.binance()

    # case 1: exchange has fetchOHLCV, timeframe, but is not in database

    # test assertions with case 1
    exchange_db_id, markets = exchange_history_load(args, ccxt_exchange)
    assert type(exchange_db_id) == int
    assert type(markets) == dict
    assert mock_get_exchange.call_count == 2
    calls = [call(mock_binance.return_value.id), call(mock_binance.return_value.id)]
    mock_get_exchange.assert_has_calls(calls)
    mock_insert_exchange_to_db.assert_called_once()
    mock_binance.return_value.load_markets.assert_called_once()

    # case 2: exchange has fetchOHLCV, timeframe, and is in database

    # reset mock calls for case 2
    mock_insert_exchange_to_db.reset_mock()
    mock_get_exchange.reset_mock()
    mock_binance.return_value.load_markets.reset_mock()

    # test assertions with case 2
    exchange_db_id, markets = exchange_history_load(args, ccxt_exchange)
    assert type(exchange_db_id) == int
    assert type(markets) == dict
    mock_get_exchange.assert_called_once()
    assert not mock_insert_exchange_to_db.called
    mock_binance.return_value.load_markets.assert_called_once()
    calls = [call(mock_binance.return_value.id)]
    mock_get_exchange.assert_has_calls(calls)

    # case 3: exchange doesn't have true fetchOHLCV


    # reset_mock calls for case 3
    mock_get_exchange.reset_mock()
    mock_insert_exchange_to_db.reset_mock()
    mock_binance.reset_mock()
    mock_binance.return_value.has.return_value = {'fetchOHLCV': True}
    # mock_binance.return_value.load_markets.reset_mock()

    # test assertions with case 3
    exchange_db_id, markets = exchange_history_load(args, ccxt_exchange)
    # assert not exchange_db_id
    # assert not markets
    assert not mock_get_exchange.called
    assert not mock_insert_exchange_to_db.called
    assert not mock_binance.return_value.load_markets.called

案例 1 和案例 2 有效。 但是對於情況 3，會拋出一個錯誤。

mock_binance = <MagicMock name='binance' id='140285596974272'>
mock_get_exchange = <MagicMock name='get_exchange' id='140285596584312'>
mock_insert_exchange_to_db = <MagicMock name='insert_exchange_to_db' id='140285596584480'>

    @patch('src.cron.historical_price.hp_load_data.insert_exchange_to_db')
    @patch('src.cron.historical_price.hp_load_data.get_exchange')
    @patch('ccxt.binance')
    def test_exchange_history_load(mock_binance, mock_get_exchange, mock_insert_exchange_to_db):
        # create sample arguments for function
        args = argparse.Namespace(timeframe='1d')

        # mock up sample return values for necessary functions
        mock_get_exchange.side_effect = [None, (1, 'binance', 'Binance'), (1, 'binance', 'Binance')]
        mock_binance.return_value.has.return_value = {'fetchOHLCV': True}
        mock_binance.return_value.load_markets.return_value = {
            'BTC/USDT': {
                'id': 'btcusdt',
                'symbol': 'BTC/USDT',
                'base': 'BTC',
                'quote': 'USDT',
                'active': True
            }
        }
        mock_binance.return_value.id.return_value = 'binance'
        mock_binance.return_value.name.return_value = 'Binance'

        ccxt_exchange = ccxt.binance()

        # case 1: exchange is not in database

        # test assertions with case 1
        exchange_db_id, markets = exchange_history_load(args, ccxt_exchange)
        assert type(exchange_db_id) == int
        assert type(markets) == dict
        assert mock_get_exchange.call_count == 2
        calls = [call(mock_binance.return_value.id), call(mock_binance.return_value.id)]
        mock_get_exchange.assert_has_calls(calls)
        mock_insert_exchange_to_db.assert_called_once()
        mock_binance.return_value.load_markets.assert_called_once()

        # case 2: exchange is in database

        # reset mock calls for case 2
        mock_insert_exchange_to_db.reset_mock()
        mock_get_exchange.reset_mock()
        mock_binance.return_value.load_markets.reset_mock()

        # test assertions with case 2
        exchange_db_id, markets = exchange_history_load(args, ccxt_exchange)
        assert type(exchange_db_id) == int
        assert type(markets) == dict
        mock_get_exchange.assert_called_once()
        assert not mock_insert_exchange_to_db.called
        mock_binance.return_value.load_markets.assert_called_once()
        calls = [call(mock_binance.return_value.id)]
        mock_get_exchange.assert_has_calls(calls)

        # case 3: exchange doesn't have true fetchOHLCV

        # reset_mock calls for case 3
        mock_get_exchange.reset_mock()
        mock_insert_exchange_to_db.reset_mock()
        mock_binance.reset_mock()
        mock_binance.return_value.has.return_value = {'fetchOHLCV': True}
        # mock_binance.return_value.load_markets.reset_mock()

        # test assertions with case 3
>       exchange_db_id, markets = exchange_history_load(args, ccxt_exchange)

test_cron/test_historical_price/test_hp_load_data.py:89: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../src/cron/historical_price/hp_load_data.py:75: in exchange_history_load
    exchange_db_data = get_exchange(ccxt_exchange.id)
/usr/lib/python3.6/unittest/mock.py:939: in __call__
    return _mock_self._mock_call(*args, **kwargs)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

_mock_self = <MagicMock name='get_exchange' id='140285596584312'>
args = (<MagicMock name='binance().id' id='140285596659328'>,), kwargs = {}
self = <MagicMock name='get_exchange' id='140285596584312'>, _new_name = ''
_new_parent = None
_call = call(<MagicMock name='binance().id' id='140285596659328'>), seen = set()
skip_next_dot = False, do_method_calls = False, name = 'get_exchange'

    def _mock_call(_mock_self, *args, **kwargs):
        self = _mock_self
        self.called = True
        self.call_count += 1
        _new_name = self._mock_new_name
        _new_parent = self._mock_new_parent

        _call = _Call((args, kwargs), two=True)
        self.call_args = _call
        self.call_args_list.append(_call)
        self.mock_calls.append(_Call(('', args, kwargs)))

        seen = set()
        skip_next_dot = _new_name == '()'
        do_method_calls = self._mock_parent is not None
        name = self._mock_name
        while _new_parent is not None:
            this_mock_call = _Call((_new_name, args, kwargs))
            if _new_parent._mock_new_name:
                dot = '.'
                if skip_next_dot:
                    dot = ''

                skip_next_dot = False
                if _new_parent._mock_new_name == '()':
                    skip_next_dot = True

                _new_name = _new_parent._mock_new_name + dot + _new_name

            if do_method_calls:
                if _new_name == name:
                    this_method_call = this_mock_call
                else:
                    this_method_call = _Call((name, args, kwargs))
                _new_parent.method_calls.append(this_method_call)

                do_method_calls = _new_parent._mock_parent is not None
                if do_method_calls:
                    name = _new_parent._mock_name + '.' + name

            _new_parent.mock_calls.append(this_mock_call)
            _new_parent = _new_parent._mock_new_parent

            # use ids here so as not to call __hash__ on the mocks
            _new_parent_id = id(_new_parent)
            if _new_parent_id in seen:
                break
            seen.add(_new_parent_id)

        ret_val = DEFAULT
        effect = self.side_effect
        if effect is not None:
            if _is_exception(effect):
                raise effect

            if not _callable(effect):
>               result = next(effect)
E               StopIteration

/usr/lib/python3.6/unittest/mock.py:998: StopIteration

Answer 1

對於那些尋求答案的人。 當您的模擬之一的side_effect在n > len(side_effect)中被調用n次時，就會出現此問題。

my_mock = MagicMock()
my_mock.side_effect = [1, 2]
...
n = 3
for i in range(n):
    my_mock()

這將觸發StopIteration錯誤。

Answer 2

您對ccxt.binance進行的Value更改導致對象ccxt_exchange超出范圍。 因此，例如，給出“ StopIteration”錯誤-

In [1]: from fleeteng_fw_agent.hostinfo imfrom mock import MagicMock, 
PropertyMock, call, patch

In [2]: mock_get_exchange = MagicMock()

In [3]: mock_get_exchange.side_effect = [None, (1, 'binance', 'Binance'), (1, 
'binance', 'Binance')]

In [4]: mock_get_exchange
Out[4]: <MagicMock id='4310663120'>

In [5]: mock_get_exchange()

In [6]: mock_get_exchange()
Out[6]: (1, 'binance', 'Binance')

In [7]: mock_get_exchange()
Out[7]: (1, 'binance', 'Binance')

In [8]: mock_get_exchange()
---------------------------------------------------------------------------
StopIteration                             Traceback (most recent call last)
<ipython-input-8-4d63b6292e10> in <module>()
----> 1 mock_get_exchange()

/Users/**/ in __call__(_mock_self, *args, **kwargs)
    954         # in the signature
    955         _mock_self._mock_check_sig(*args, **kwargs)
--> 956         return _mock_self._mock_call(*args, **kwargs)
    957 
    958 

/Users/**/ in _mock_call(_mock_self, *args, **kwargs)
   1012 
   1013             if not _callable(effect):
-> 1014                 result = next(effect)
   1015                 if _is_exception(result):
   1016                     raise result

StopIteration: 

我將需要查看ccxt.binancegive的值更改，以為您提供確切的錯誤原因。 但我認為上述示例應將您引導到根本原因。