Python 3 urlopen 上下文管理器模拟 [英] Python 3 urlopen context manager mocking

问题描述

我是测试新手，需要一些帮助.

I am new to testing and need some help here.

假设有这个方法:

from urllib.request import urlopen

def get_posts():
    with urlopen('some url here') as data:
        return json.loads(data.read().decode('utf-8'))

问题是如何测试这个方法(如果可能，使用 mock.patch 装饰器)?

The question is how to test this method (using mock.patch decorator if possible)?

我现在拥有的:

@mock.patch('mymodule.urlopen')
def test_get_post(self, mocked_urlopen):
    mocked_urlopen.__enter__ = Mock(return_value=self.test_data)
    mocked_urlopen.__exit__ = Mock(return_value=False)
    ...

但它似乎不起作用.

附言有没有什么方便的方法可以在测试中使用数据变量(哪种类型是 HTTPResponse)，以便它可以只是简单的字符串?

P.S. Is there any convenient way to work with data variable (which type is HTTPResponse) in test so it could just be simple string?

推荐答案

好的，我写了一个简单的类来模拟上下文管理器.

Ok, so I have written simple class to simulate context manager.

class PatchContextManager:

    def __init__(self, method, enter_return, exit_return=False):
        self._patched = patch(method)
        self._enter_return = enter_return
        self._exit_return = exit_return

    def __enter__(self):
        res = self._patched.__enter__()
        res.context = MagicMock()
        res.context.__enter__.return_value = self._enter_return
        res.context.__exit__.return_value = self._exit_return
        res.return_value = res.context
        return res

    def __exit__(self, type, value, tb):
        return self._patched.__exit__()

用法:

with PatchContextManager('mymodule.method', 'return_string') as mocked:
    a = mymodule.method(47) # a == 'return_string'
    mocked.assert_called_with(47)
    ... 

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