模拟方法调用 Python

Question

我一直在搜索堆栈交换和网络以了解如何执行此操作，但我不明白如何模拟方法的行为。我正在尝试为我的自定义 class 模拟 openpyxl 行为和行为。这是我的尝试：

import unittest
from unittest.mock import MagicMock
import openpyxl 
from MyPythonFile import MyClass

class TestMyClass(unittest.TestCase):
  def test_myclass(self):
    myclass = MyClass()
    wb = openpyxl.workbook()
    ws = openpyxl.worksheet()
    wbPath = 'wbPath'

    openpyxl.load_workbook(wbPath, data_only = True) = MagicMock(return_value=wb)

当我尝试最后一行时，出现错误 "can't assign to function call"。我需要使用 patch.object('openpyxl','load_workbook') 吗？我习惯于在 Java 中使用 Groovy 进行模拟，这非常简单。

*编辑：想根据@alxwrd

的回复添加测试的最终版本

import unittest
from unittest.mock import MagicMock
import openpyxl 
import configparser
from MyPythonFile import MyClass

class TestMyClass(unittest.TestCase):
  def test_myclass(self):
    myclass = MyClass()
    wb = openpyxl.workbook()
    ws = openpyxl.worksheet()
    config = configparser.ConfigParser()

    openpyxl.load_workbook = MagicMock(return_value=wb)
    wb.get_sheet_by_name = MagicMock(return_value=ws)

    config.sections() = MagicMock(return_value=['Section1'])
    config.get = MagicMock(side_effect=['Value1','Value2'])

注意 config.get 给出多个 returns 与 side_effect 参数，所以如果 config.get() 在代码中调用一次它 returns 'Value1' 并且当 config.get() 被第二次调用时 returns 'Value2'.

Answer 1

您无法覆盖函数调用，但您可以覆盖函数本身。

来自docs：

>>> from unittest.mock import MagicMock
>>> thing = ProductionClass()
>>> thing.method = MagicMock(return_value=3)
>>> thing.method(3, 4, 5, key='value')
3
>>> thing.method.assert_called_with(3, 4, 5, key='value')

所以在你的情况下：

openpyxl.load_workbook = MagicMock(return_value=wb)

Answer 2

您不必在单元测试中导入要模拟的目标。使用 patch to mock the target. Let's assume your code has this import statement: import openpyxl. Patch then can be used in your test as a decorator:

import unittest
from unittest import mock
from MyPythonFile import MyClass

class TestMyClass(unittest.TestCase):

    @mock.patch('MyPythonFile.openpyxl')
    def test_myclass(self, openpyxl_mock):
        wb_dummy = 'foo'
        openpyxl_mock.load_workbook.return_value = wb_dummy

        myclass = MyClass()
        myclass.load_workbook()  # assuming this calls openpyxl.load_workbook()

请注意，您必须向将获取模拟对象的测试方法添加一个参数。

或作为 context manager:

import unittest
from unittest import mock
from MyPythonFile import MyClass

class TestMyClass(unittest.TestCase):

    def test_myclass(self):
        with mock.patch('MyPythonFile.openpyxl') as openpyxl_mock:
            wb_dummy = 'foo'
            openpyxl_mock.load_workbook.return_value = wb_dummy

            myclass = MyClass()
            myclass.load_workbook()  # assuming this calls openpyxl.load_workbook()

模拟方法调用 Python

Mocking Method Calls In Python

python

methods

unit-testing

mocking

configparser