模拟 - 修补类方法以引发异常

Question

这是我尝试使用 mock 测试的代码的通用示例。我得到一个 AttributeError。

这里是 __init__.py：

import logging
log = logging.getLogger(__name__)

class SomeError(Exception):
    pass

class Stuff(object):
    # stub

    def method_a(self):
        try:
            stuff = self.method_b()
        except SomeError, e:
            log.error(e)
            # show a user friendly error message
            return 'no ponies'
        return 'omg ponies'

    def method_b(self):
        # can raise SomeError
        return ''

在 tests.py 我有这样的东西：

import mock
import unittest

from package.errors import SomeError
from mypackage import Stuff

some_error_mock = mock.Mock()
some_error_mock.side_effect = SomeError

class MyTest(unittest.TestCase):

    @mock.patch.object('Stuff', 'method_b', some_error_mock)
    def test_some_error(self):
        # assert that method_a handles SomeError correctly
        mystuff = Stuff()
        a = mystuff.method_a()
        self.assertTrue(a == 'no ponies')

运行测试时，mock 会引发 AttributeError 说：“Stuff does not have the attribute 'method_b'”

我在这里做错了什么？

Answer 1

装饰器第一个参数应该是对象的类，你误用了类名的字符串

@mock.patch.object('Stuff', 'method_b', some_error_mock)

应该变成

@mock.patch.object(Stuff, 'method_b', some_error_mock)

http://docs.python.org/dev/library/unittest.mock#patch-object