如何模拟在 with 语句中使用的 open (使用 Python 中的 Mock 框架)?

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

推荐答案

mock 0.7.0 改变了这样做的方式，最终支持模拟 python 协议方法(魔术方法)，特别是使用 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

作为上下文管理器模拟打开的示例(来自模拟文档中的示例页面):

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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