Python:模拟上下文管理器 [英] Python: Mocking a context manager

问题描述

我不明白为什么在此示例中无法模拟NamedTemporaryFile.name:

I don't understand why I can't mock NamedTemporaryFile.name in this example:

from mock import Mock, patch
import unittest
import tempfile

def myfunc():
    with tempfile.NamedTemporaryFile() as mytmp:
        return mytmp.name

class TestMock(unittest.TestCase):
    @patch('tempfile.NamedTemporaryFile')
    def test_cm(self, mock_tmp):
        mytmpname = 'abcde'
        mock_tmp.__enter__.return_value.name = mytmpname
        self.assertEqual(myfunc(), mytmpname)

测试结果:

AssertionError: <MagicMock name='NamedTemporaryFile().__enter__().name' id='140275675011280'> != 'abcde'

推荐答案

您设置了错误的模拟:mock_tmp不是上下文管理器，而是返回.将您的设置行替换为:

You are setting the wrong mock: mock_tmp is not the context manager, but instead returns a context manager. Replace your setup line with:

mock_tmp.return_value.__enter__.return_value.name = mytmpname

您的测试将起作用.

这篇关于Python:模拟上下文管理器的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！