我如何在模拟类中模拟/修补多种方法？

Question

我对Python自动测试没有经验，并且尝试嘲笑（或补丁？）类及其一些方法，我非常困难。

这是我们的文件夹结构：

src
|--- main
     |--- run_data_process.py
tests
|--- main_tests
     |--- test_run_data_process.py

下面是到目前为止这些文件的一些代码：

run_data_process.py ：

import logging
import pandas as pd
import sys

from company.connections import DBConnection # internal library from my company
from company.data_tools import DataStorageManager # another internal library

logger = logging.getLogger(__name__)


class DataProcessException(Exception):
    pass


class DataProcess:
    def run_task(self):
        try:
            df_raw = self.gather_data()
            self.validate_gathered_data(df_raw)
        except DataProcessException as e:
            logger.error(f"Error on the Data Process task: {e}")
            raise
        else:
            self.save_output_data(df_raw)
            logger.info("Data Process task executed successfully.")

    def gather_data(self) -> pd.DataFrame:
        """This calls the database and returns a DataFrame. I don't have access to the implementation of DBConnection()."""
        conn = DBConnection()
        return conn.run()

    def validate_gathered_data(self, df_raw: pd.DataFrame) -> None:
        if len(df_raw) == 0:
            raise DataProcessException("Raw dataset is empty.")

    def save_output_data(self, df_raw: pd.DataFrame) -> None:
        """Another internal library that serialises the DataFrame and sends it to another server. Don't have the implementation either."""
        DataStorageManager().save_output_object(df_raw)

test_run_data_process.py ：

from unittest.mock import Mock, MagicMock, patch
import pandas as pd
import pytest

from src.main.run_data_process import DataProcess, RawDataException


class TestDataProcess:

    def __get_mocked_dataset():
        return pd.DataFrame(
            [[111, 222, 333], ['text_1', 'text_2', 'text_3'], [True, False, False]],
            columns=['col_1', 'col_2', 'col_3'])

    def test_gathered_data_is_validated_successfully(self):
        # arrange / act
        with patch('src.main.run_data_process.DataProcess', return_value=MagicMock()) as p:
            p.return_value.gather_data = Mock(return_value=self.__get_mocked_dataset)
            p.return_value.save_output_data = Mock(return_value=None)
            p.return_value.run_task()

        # assert
        p.return_value.validate_gathered_data.assert_called_with(p.return_value.gather_data.return_value)

我要做的是test 嘲笑 gather_data validate_gathered_data save_output_data （要避免调用我们的服务器），但是我无法使其正常工作，我将头发拉出来。

上面的代码给了我一个错误：

./tests/main_tests/test_run_data_process.py::TestDataProcess::test_gathered_data_is_validated_successfully Failed: [undefined]AssertionError: expected call not found.
Expected: validate_gathered_data(<bound method TestDataProcess.__get_mocked_dataset of <tests.main_tests.test_run_data_process.TestDataProcess object at 0x123b9fe50>>)
Actual: not called.
__wrapped_mock_method__ = <function NonCallableMock.assert_called_with at 0x108964550>
args = (<MagicMock name='mock.validate_gathered_data' id='4894604448'>, <bound method TestDataProcess.__get_mocked_dataset of <tests.main_tests.test_run_data_process.TestDataProcess object at 0x123b9fe50>>)
kwargs = {}, __tracebackhide__ = True
msg = 'expected call not found.\nExpected: validate_gathered_data(<bound method TestDataProcess.__get_mocked_dataset of <tests.main_tests.test_run_data_process.TestDataProcess object at 0x123b9fe50>>)\nActual: not called.'
__mock_self = <MagicMock name='mock.validate_gathered_data' id='4894604448'>

    def assert_wrapper(
        __wrapped_mock_method__: Callable[..., Any], *args: Any, **kwargs: Any
    ) -> None:
        __tracebackhide__ = True
        try:
>           __wrapped_mock_method__(*args, **kwargs)

../../../../Library/Python/3.8/lib/python/site-packages/pytest_mock/plugin.py:414: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <MagicMock name='mock.validate_gathered_data' id='4894604448'>
args = (<bound method TestDataProcess.__get_mocked_dataset of <tests.main_tests.test_run_data_process.TestDataProcess object at 0x123b9fe50>>,)
kwargs = {}
expected = 'validate_gathered_data(<bound method TestDataProcess.__get_mocked_dataset of <tests.main_tests.test_run_data_process.TestDataProcess object at 0x123b9fe50>>)'
actual = 'not called.'
error_message = 'expected call not found.\nExpected: validate_gathered_data(<bound method TestDataProcess.__get_mocked_dataset of <tests.main_tests.test_run_data_process.TestDataProcess object at 0x123b9fe50>>)\nActual: not called.'

    def assert_called_with(self, /, *args, **kwargs):
        """assert that the last call was made with the specified arguments.
    
        Raises an AssertionError if the args and keyword args passed in are
        different to the last call to the mock."""
        if self.call_args is None:
            expected = self._format_mock_call_signature(args, kwargs)
            actual = 'not called.'
            error_message = ('expected call not found.\nExpected: %s\nActual: %s'
                    % (expected, actual))
>           raise AssertionError(error_message)
E           AssertionError: expected call not found.
E           Expected: validate_gathered_data(<bound method TestDataProcess.__get_mocked_dataset of <tests.main_tests.test_run_data_process.TestDataProcess object at 0x123b9fe50>>)
E           Actual: not called.

/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/unittest/mock.py:904: AssertionError

During handling of the above exception, another exception occurred:

self = <tests.main_tests.test_run_data_process.TestDataProcess object at 0x123b9fe50>

    def test_gathered_data_is_validated_successfully(self):
        # arrange / act
        with patch('src.main.run_data_process.DataProcess', return_value=MagicMock()) as p:
            p.return_value.gather_data = Mock(return_value=self.__get_mocked_dataset)
            p.return_value.save_output_artifact = Mock(return_value=None)
            p.return_value.run_task()
    
        # assert
>       p.return_value.validate_gathered_data.assert_called_with(p.return_value.gather_data.return_value)
E       AssertionError: expected call not found.
E       Expected: validate_gathered_data(<bound method TestDataProcess.__get_mocked_dataset of <tests.main_tests.test_run_data_process.TestDataProcess object at 0x123b9fe50>>)
E       Actual: not called.

tests/main_tests/test_run_data_process.py:23: AssertionError

在我以前的拍摄中，我已经尝试了@mock.patch.multiple 在实例化 dataprocess （一种解决方案，在这里看到的较旧的，无数的问题），但被卡在 assert_called_with part上。

任何帮助将不胜感激。

Answer 1

通常会更好/更容易避免修补测试的类，而是在测试的模块中修补其依赖项（在需要的情况下）。

在这种情况下，由于您要避免实例化的特定内容是 dbConnection 和 datastoragemanager ，因此直接的解决方案是只需修补 dbConnection 和 datastoragemanager ：

    @patch('src.main.run_data_process.DataStorageManager')
    @patch('src.main.run_data_process.DBConnection')
    def test_gathered_data_is_validated_successfully(self, db, storage):
        db().run.return_value = self.__get_mocked_dataset()
        DataProcess().run_task()
        assert storage().save_output_object.call_count == 1

记住 patch（）默认情况下创建 MagicMock MagicMock上的属性查找还默认创建 MagicMock （在后续呼叫上重复使用），因此您可以通过简单地访问访问模拟来轻松地在模拟上设置一堆属性它们就像您的代码一样 - 在这种情况下，模拟对象表示类测试的代码调用的实例。