如何模拟with语句中使用的打开(使用Python中的Mock框架)? [英] How do I mock an open used in a with statement (using the Mock framework in Python)?

问题描述

如何使用模拟测试以下代码(使用模拟，补丁装饰器和 Michael Foord的Mock框架):

How do I test the following code with mocks (using mocks, the patch decorator and sentinels provided by Michael Foord's Mock framework):

def testme(filepath):
    with open(filepath, 'r') as f:
        return f.read()

推荐答案

此方法已在模拟0.7.0中更改，该模拟最终支持模拟python协议方法(魔术方法)，尤其是使用MagicMock:

The way to do this has changed in mock 0.7.0 which finally supports mocking the python protocol methods (magic methods), particularly using the MagicMock:

http://www.voidspace.org.uk/python/mock/magicmock.html

作为上下文管理器打开的模拟示例(来自模拟文档的示例页面):

An example of mocking open as a context manager (from the examples page in the mock documentation):

>>> open_name = '%s.open' % __name__
>>> with patch(open_name, create=True) as mock_open:
...     mock_open.return_value = MagicMock(spec=file)
...
...     with open('/some/path', 'w') as f:
...         f.write('something')
...
<mock.Mock object at 0x...>
>>> file_handle = mock_open.return_value.__enter__.return_value
>>> file_handle.write.assert_called_with('something')

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