How to check if all files were closed using Mock

test_files.py

import mock
files_opened = []
real_open = open   # Needed since I will wrap open
def open_wrapper(*args, **kw):
    opened_file = mock.MagicMock(wraps=real_open(*args, **kw))
    files_opened.append(opened_file)
    return opened_file
open_mock = mock.MagicMock(side_effect=open_wrapper)
open_mock.__enter__.side_effect = open_wrapper

with mock.patch('__builtin__.open', open_mock, create=True):
    import myapplication
    myapplication.run()

for opened_file in files_opened:
    opened_file.close.assert_called_once_with()

@has207 Always fun to see it in another implementation. Seems like this is (currently) one of those things that are still a little clumsy. The things is, it's a highly useful test to catch all those file not closed. I am surprised this problem has surfaces before.