mock.MagicMock does not mock __truediv__

[JohannesBaiter]

BPO	20968
Nosy	@rhettinger, @voidspace
Files	mock_truediv.diff: Make unittest.mock.MagicMock mock truediv and rtruediv mock_truediv_numerics.diff: Add 'truediv' to global 'numerics' instead of 'magic_methods' mock_truediv_with_tests.diff: Add tests

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/voidspace'
closed_at = <Date 2014-04-14.15:44:42.196>
created_at = <Date 2014-03-18.14:13:34.429>
labels = ['type-bug', 'library']
title = 'mock.MagicMock does not mock __truediv__'
updated_at = <Date 2014-04-14.15:44:42.195>
user = 'https://bugs.python.org/JohannesBaiter'

bugs.python.org fields:

activity = <Date 2014-04-14.15:44:42.195>
actor = 'michael.foord'
assignee = 'michael.foord'
closed = True
closed_date = <Date 2014-04-14.15:44:42.196>
closer = 'michael.foord'
components = ['Library (Lib)']
creation = <Date 2014-03-18.14:13:34.429>
creator = 'Johannes.Baiter'
dependencies = []
files = ['34490', '34491', '34515']
hgrepos = []
issue_num = 20968
keywords = ['patch']
message_count = 10.0
messages = ['213964', '213968', '213973', '214077', '214083', '214084', '215228', '215357', '216094', '216101']
nosy_count = 4.0
nosy_names = ['rhettinger', 'michael.foord', 'python-dev', 'Johannes.Baiter']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue20968'
versions = ['Python 3.4']

[JohannesBaiter]

It seems that when creating a MagicMock the magic '__truediv__' method is not replaced with a mock:

>>> import mock
>>> foo = mock.MagicMock()
>>> foo / 2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for /: 'MagicMock' and 'int'

The same thing works perfectly fine when using the third party module in Python 2.7, since the 2.x '__div__' seems to be mocked:

>>> import mock
>>> foo = mock.MagicMock()
>>> foo/2
<MagicMock name='mock.__div__()' id='139760595027088'>

To clarify the context, I am trying to mock a 'pathlib.Path' object in my unittest, which overloads the division operator, i.e. implements '__truediv__'.

[JohannesBaiter]

Attached is a patch that fixes the issue for me.

[JohannesBaiter]

I just noticed that I put the magic method names in the wrong place in the patch.
Attached is a fix that adds 'truediv' to the global 'numberics' variable, this way '__rtruediv__' and '__itruediv__' will be correctly mocked as well.

[voidspace]

A test would be nice please (good catch on the bug).

[JohannesBaiter]

From looking at 'test_numerics', only 'add' is currently tested.
Probably since the mechanism for all of the numeric magic methods is the same (i.e. create __<op>, __i<op>, __r<op>__).

Should I add a test for __truediv__ and its inplace and right variants nonetheless?

[voidspace]

Well, as this is a regression fix we definitley need a test. Ideally we would test all the operations - I didn't realise that only add was tested! However for this specific issue, just testing division is fine, and yes testing in place and right hand as well would be good.

[JohannesBaiter]

Sorry for commenting so late, I submitted a version of the patch with unit tests roughly two weeks ago, I just forgot to mention it in a comment. Hereby fixed :-)

[rhettinger]

The patch looks clean and correct. It passes the test suite.

I recommend going ahead and applying the patch.

[python-dev]

New changeset 445ef3b58109 by Michael Foord in branch '3.4':
bpo-20968. unittest.mock.MagicMock now supports division
http://hg.python.org/cpython/rev/445ef3b58109

[voidspace]

Thanks!