Python模拟中的Mock属性？

Question

我mock在Python中使用起来相当困难:

def method_under_test():
    r = requests.post("http://localhost/post")

    print r.ok # prints "<MagicMock name='post().ok' id='11111111'>"

    if r.ok:
       return StartResult()
    else:
       raise Exception()

class MethodUnderTestTest(TestCase):

    def test_method_under_test(self):
        with patch('requests.post') as patched_post:
            patched_post.return_value.ok = True

            result = method_under_test()

            self.assertEqual(type(result), StartResult,
                "Failed to return a StartResult.")

测试实际上返回正确的值,但是r.ok是Mock对象,而不是True.你如何在Python的mock库中模拟属性？

Answer 1

你需要使用return_value和PropertyMock:

with patch('requests.post') as patched_post:
    type(patched_post.return_value).ok = PropertyMock(return_value=True)

这意味着:在调用时requests.post,在该调用的返回值上,PropertyMock为属性设置a ok以返回该值True.

Answer 2

一种紧凑而简单的方法是使用new_callable patch's属性强制patch使用PropertyMock而不是MagicMock创建模拟对象.传递给的其他参数patch将用于创建PropertyMock对象.

with patch('requests.post', new_callable=PropertyMock, return_value=True) as mock_post:
    """Your test"""

Answer 3

使用模拟版本'1.0.1',问题中提到的更简单的语法是支持的,并按原样工作!

示例代码已更新(使用py.test而不是unittest):

import mock
import requests


def method_under_test():
    r = requests.post("http://localhost/post")

    print r.ok

    if r.ok:
        return r.ok
    else:
        raise Exception()


def test_method_under_test():
    with mock.patch('requests.post') as patched_post:
        patched_post.return_value.ok = True

        result = method_under_test()
        assert result is True, "mock ok failed"

运行此代码:(确保安装pytest)

$ py.test -s -v mock_attributes.py 
======= test session starts =======================
platform linux2 -- Python 2.7.10 -- py-1.4.30 -- pytest-2.7.2 -- /home/developer/miniconda/bin/python
rootdir: /home/developer/projects/learn/scripts/misc, inifile: 
plugins: httpbin, cov
collected 1 items 

mock_attributes.py::test_method_under_test True
PASSED

======= 1 passed in 0.03 seconds =================