Python 模拟、补丁 os.environ 返回 None

Question

我有一个简单的模块:

# my_module
from os.path import join
from os import environ

some_file_name = 'foo.txt'

def file_path():
    join(environ['TARGET_DIRECTORY'], some_file_name)

还有一个简单的测试:

import os
import unittest
from os.path import join

from mock import patch
from my_module import some_file_name, file_path


class MyTest(unittest.TestCase):
    def test_can_create_path(self):
        some_folder = '/path/to/directory'
        with patch.dict('my_module.environ', {'TARGET_DIRECTORY': some_folder}):
            self.assertEqual(file_path(), join(some_folder, some_file_name))

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

我预计对 environ['TARGET_DIRECTORY'] 的调用会返回 '/path/to/directory' 但它返回 None

Answer 1

您的函数返回None，因为没有显式的return语句。添加返回:

def file_path():
    return join(environ['TARGET_DIRECTORY'], some_file_name)

模拟补丁在其他方面工作正常。