Python Mock中的Mock属性

Question

我在Python中使用mock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是一个Mock对象，而不是True。如何在Python的mock库中模拟属性?

Answer 1

您需要使用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:当调用requests.post时，在该调用的返回值上，为属性ok设置PropertyMock以返回值True。

Answer 2

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

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

Answer 3

对于模拟版本'1.0.1'，问题中提到的更简单的语法得到了支持，并且可以正常工作!

示例代码更新(py。使用Test代替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"

运行下面的代码:(确保你安装了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 =================