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Message #70806
[Bug 1735588] Re: Mock autospec not used, or not used properly
** Also affects: compute-hyperv
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1735588
Title:
Mock autospec not used, or not used properly
Status in compute-hyperv:
New
Status in networking-hyperv:
Fix Released
Status in OpenStack Compute (nova):
In Progress
Status in os-win:
Fix Released
Status in oslotest:
Fix Released
Bug description:
Description
===========
In typical unit tests, almost all of the dependencies are mocked or
patched (mock.patch), without any guarantee that the mocked methods
actually exist, or if their signatures are respected (see below).
Because of this, actual issues can easily be overlooked and missed, as
the unit tests are wrongfully passing. [0]
The mock.Mock class accepts a spec as an argument, which only solves
half the problem: it only checks if an attribute exists, based on the
given spec. It does not guarantee that the given attribute is actually
a method, or if its signature is respected [1][2]. Some unit tests may
pass the autospec argument, but mock doesn't support it at the moment.
mock.patch, mock.patch.object, mock.patch.multiple accept an autospec
argument, but because of a bug [3][4], it cannot be used properly.
Steps to reproduce
==================
import mock
from mock.tests import testmock
m = mock.Mock(spec=testmock.Something)
# meth has the following signature:
# def meth(self, a, b, c, d=None):
m.meth()
Expected result
===============
TypeError should be raised.
Actual result
=============
A mock object is returned.
Proposal
========
Bug reports have been issues for the bugs mentioned above, see
[1][2][3][4], but until then, the mock library can be patched to
include the following changes:
- add autospec argument to mock.Mock and mock.MagicMock. Unit test should then pass the autospec argument whenever possible.
- fix the mock.patch autospec issue.
- enable mock.patch autospec by default, unless otherwise specified.
Links
=====
[0] https://review.openstack.org/#/c/461689/
[1] https://github.com/testing-cabal/mock/issues/393
[2] https://bugs.python.org/issue30587
[3] https://github.com/testing-cabal/mock/issues/396
[4] https://bugs.python.org/issue32092
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References