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python - Mock 在 Python 2.7 的单元测试中不起作用

问题描述

我有一个这样的项目结构：

py_test
   |
   +---my_module
   |    |  
   |    +--- __init__.py (empty)
   |    |
   |    +--- futil.py
   |
   +---test
        |
        +--- __init__.py (empty)
        |
        +--- futil_test.py

在futil.py我有以下内容：

from os import path


def check_exists(file_path):
    return path.exists(file_path)

在futil_test.py我试图实现这样的单元测试：

import mock
import unittest

from my_module.futil import check_exists


class TestExists(unittest.TestCase):

    @mock.patch('my_module.futil.os.path')        # <---leads to error, as well as my_module.os.path
    def test_exists(self, mock_path):
        mock_path.exists.return_value = True
        self.assertTrue(check_exists('ba'))


if __name__ == '__main__':
    unittest.main()

当我尝试启动单元测试时，它失败并出现错误：

Error
Traceback (most recent call last):
  File "/usr/lib64/python2.7/unittest/case.py", line 367, in run
    testMethod()
  File "/home/antonio/devel/py/py_test/venv/lib/python2.7/site-packages/mock/mock.py", line 1322, in patched
    arg = patching.__enter__()
  File "/home/antonio/devel/py/py_test/venv/lib/python2.7/site-packages/mock/mock.py", line 1378, in __enter__
    self.target = self.getter()
  File "/home/antonio/devel/py/py_test/venv/lib/python2.7/site-packages/mock/mock.py", line 1548, in <lambda>
    getter = lambda: _importer(target)
  File "/home/antonio/devel/py/py_test/venv/lib/python2.7/site-packages/mock/mock.py", line 1235, in _importer
    thing = _dot_lookup(thing, comp, import_path)
  File "/home/antonio/devel/py/py_test/venv/lib/python2.7/site-packages/mock/mock.py", line 1224, in _dot_lookup
    __import__(import_path)
ImportError: No module named os

在此处的示例中，类似的构造似乎正在起作用。我究竟做错了什么？

标签： pythonpython-2.7unit-testing

解决方案

“from os import path”，将使路径功能成为 futil 的一部分。而不是模拟“my_module.futil.os.path'”只是模拟“my_module.futil.path'”，应该可以。

我发现这篇文章在过去非常有用http://alexmarandon.com/articles/python_mock_gotchas/

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