python-mock: 'self' parameter lacking defa

Question

This used to work with python mock version 1.0.1, but started failing after I upgraded to mock version 1.3.0. I am running python version 2.7.10 on Mac OS X Yosemite 10.10.5.

I reduced the logic from an existing production test to the following dummy test that reproduces the issue:

import unittest

import mock
from mock import Mock, patch

class Outer(object):
    class MyClass(object):

        def doStuff(self, action):
            pass

@patch.object(Outer, "MyClass", autospec=True,
              return_value=Mock(spec_set=Outer.MyClass, 
                                doStuff=Mock(spec_set=Outer.MyClass.doStuff)))
class MyTestCase(unittest.TestCase):
    def testDoStuff(self, myClassMock):
        obj = myClassMock()
        obj.doStuff(action="swim")
        obj.doStuff.assert_called_once_with(action="swim")

The failure output looks like this:

$ py.test -v new_mock_test.py 
====================================================================================== test session starts =======================================================================================
platform darwin -- Python 2.7.10, pytest-2.8.5, py-1.4.30, pluggy-0.3.1 -- /System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python
cachedir: .cache
rootdir: /Users/me/TempOnDesktop, inifile: 
plugins: cov-1.6, xdist-1.8
collected 1 items 

new_mock_test.py::MyTestCase::testDoStuff FAILED

============================================================================================ FAILURES ============================================================================================
_____________________________________________________________________________________ MyTestCase.testDoStuff _____________________________________________________________________________________

self = <new_mock_test.MyTestCase testMethod=testDoStuff>, myClassMock = <MagicMock name='MyClass' spec='MyClass' id='4367040848'>

    def testDoStuff(self, myClassMock):

        obj = myClassMock()

        obj.doStuff(action="swim")

>     obj.doStuff.assert_called_once_with(action="swim")

new_mock_test.py:26: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../Library/Python/2.7/lib/python/site-packages/mock/mock.py:948: in assert_called_once_with
    return self.assert_called_with(*args, **kwargs)
../Library/Python/2.7/lib/python/site-packages/mock/mock.py:937: in assert_called_with
    six.raise_from(AssertionError(_error_message(cause)), cause)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

value = AssertionError("Expected call: doStuff(action='swim')\nActual call: doStuff(action='swim')\n'self' parameter lacking default value",)
from_value = TypeError("'self' parameter lacking default value",)

    def raise_from(value, from_value):
>       raise value
E       AssertionError: Expected call: doStuff(action='swim')
E       Actual call: doStuff(action='swim')
E       'self' parameter lacking default value

../Library/Python/2.7/lib/python/site-packages/six.py:718: AssertionError
========================================================================== 1 failed, 2 pytest-warnings in 0.13 seconds ===========================================================================

Answer 1

Ommit spec_set (and spec) on instance method mock of Outer.MyClass.doStuff. The self will not be captured/asserted by assert_called_once_with and your test will pass.

    @patch.object(Outer, "MyClass", autospec=True,
          return_value=Mock(spec_set=Outer.MyClass, 
                            doStuff=Mock()))