问题描述
我有一个函数 (foo),它调用另一个函数 (bar).如果调用bar()引发了HttpError,如果状态码是404我想特别处理,否则重新引发.
I have a function (foo) which calls another function (bar). If invoking bar() raises an HttpError, I want to handle it specially if the status code is 404, otherwise re-raise.
我正在尝试围绕这个 foo 函数编写一些单元测试,模拟对 bar() 的调用.不幸的是,我无法获得对 bar() 的模拟调用来引发我的 except 块捕获的异常.
I am trying to write some unit tests around this foo function, mocking out the call to bar(). Unfortunately, I am unable to get the mocked call to bar() to raise an Exception which is caught by my except block.
这是说明我的问题的代码:
Here is my code which illustrates my problem:
import unittest import mock from apiclient.errors import HttpError class FooTests(unittest.TestCase): @mock.patch('my_tests.bar') def test_foo_shouldReturnResultOfBar_whenBarSucceeds(self, barMock): barMock.return_value = True result = foo() self.assertTrue(result) # passes @mock.patch('my_tests.bar') def test_foo_shouldReturnNone_whenBarRaiseHttpError404(self, barMock): barMock.side_effect = HttpError(mock.Mock(return_value={'status': 404}), 'not found') result = foo() self.assertIsNone(result) # fails, test raises HttpError @mock.patch('my_tests.bar') def test_foo_shouldRaiseHttpError_whenBarRaiseHttpErrorNot404(self, barMock): barMock.side_effect = HttpError(mock.Mock(return_value={'status': 500}), 'error') with self.assertRaises(HttpError): # passes foo() def foo(): try: result = bar() return result except HttpError as error: if error.resp.status == 404: print '404 - %s' % error.message return None raise def bar(): raise NotImplementedError()
我按照 Mock docs 说您应该将 Mock 实例的 side_effect 设置为 Exception 类,以使模拟函数引发错误.
I followed the Mock docs which say that you should set the side_effect of a Mock instance to an Exception class to have the mocked function raise the error.
我还查看了一些其他相关的 StackOverflow Q&As,看起来我正在做与他们正在做的事情相同的事情,以导致他们的模拟引发异常.
I also looked at some other related StackOverflow Q&As, and it looks like I am doing the same thing they are doing to cause and Exception to be raised by their mock.
- https://stackoverflow.com/a/10310532/346561
- 如何使用 Python Mock 引发异常 - 但将 Errno 设置为给定值
为什么设置 barMock 的 side_effect 不会引发预期的 Exception?如果我在做一些奇怪的事情,我应该如何在我的 except 块中测试逻辑?
Why is setting the side_effect of barMock not causing the expected Exception to be raised? If I am doing something weird, how should I go about testing logic in my except block?
推荐答案
你的 mock 可以很好地引发异常,但是缺少 error.resp.status 值.与其使用 return_value,不如告诉 Mock status 是一个属性:
Your mock is raising the exception just fine, but the error.resp.status value is missing. Rather than use return_value, just tell Mock that status is an attribute:
barMock.side_effect = HttpError(mock.Mock(status=404), 'not found')
Mock() 的附加关键字参数被设置为结果对象的属性.
Additional keyword arguments to Mock() are set as attributes on the resulting object.
我将您的 foo 和 bar 定义放在 my_tests 模块中,并添加到 HttpError class 所以我可以使用它也一样,然后你的测试就可以成功了:
I put your foo and bar definitions in a my_tests module, added in the HttpError class so I could use it too, and your test then can be ran to success:
>>> from my_tests import foo, HttpError >>> import mock >>> with mock.patch('my_tests.bar') as barMock: ... barMock.side_effect = HttpError(mock.Mock(status=404), 'not found') ... result = my_test.foo() ... 404 - >>> result is None True
您甚至可以看到 print '404 - %s' % error.message 行运行,但我认为您想在那里使用 error.content ;无论如何,这就是 HttpError() 从第二个参数设置的属性.
You can even see the print '404 - %s' % error.message line run, but I think you wanted to use error.content there instead; that's the attribute HttpError() sets from the second argument, at any rate.