[feature-request] Set default mock class

[GoogleCodeExporter]

Hi!

I made my own small mock class and I love it:

class RVDescriptor(object):
    def __get__(self, instance, owner):
        if instance is None:
            return owner.return_value
        return instance.return_value

    def __set__(self, instance, value):
        instance.return_value = value

    def __delete__(self, instance):
        del instance.return_value

class M(MagicMock):
    """
    :class:`~MagicMock` with shortcuts. I just couldn't stand the
    ``.return_value.foo.return_value.bar.return_value`` thing.
    """
    def __init__(self, *args, **kw):
        super(M, self).__init__(*args, **kw)

    def _get_child_mock(self, **kw):
        return M(**kw)

    rv = RVDescriptor()

But still, when I do patch -- I will get MagicMock (or Mock), not M(). Can that 
somehow be fixed? Thanks.

Original issue reported on code.google.com by k...@k-bx.com on 22 Mar 2012 at 5:33

[GoogleCodeExporter]

Also then I would get enough willing to end up with implementation of my 
.assert_filtered_by thing, because right now it is ugly, I would like to see it 
as mock property, not a function (you can see example here 
http://www.redhotchilipython.com/en_posts/testing_python/09-django-specific-test
ing.html ).

Thanks!

Original comment by k...@k-bx.com on 22 Mar 2012 at 5:35

[GoogleCodeExporter]

By the way, you shouldn't need either your __init__ or your _child_mock. Your 
__init__ is empty (so the default would be identical), and _get_child_mock will 
use the class of the parent mock by default as well.

Original comment by fuzzyman on 23 Mar 2012 at 12:16

• Added labels: Type-Enhancement
• Removed labels: Type-Defect

[GoogleCodeExporter]

Oh, nice to know that, thanks! I'll just throw away them, then.

Original comment by k...@k-bx.com on 23 Mar 2012 at 3:05

[GoogleCodeExporter]

Oh, yeah, I don't even remember why did I wrote the __init__ in a first place 
:) it doesn't actually do anything.

Original comment by k...@k-bx.com on 23 Mar 2012 at 3:06

[GoogleCodeExporter]

I don't think a change is needed to mock to support this, writing your own 
wrapper round patch to do this is trivial:

>>> from mock import patch, DEFAULT, MagicMock
>>> class MyMock(MagicMock): pass
... 
>>> def my_patch(target, new=DEFAULT, spec=None, create=False, spec_set=None, 
autospec=None, new_callable=None, **kwargs):
...  if new is DEFAULT and new_callable is None:
...   new_callable = MyMock
...  return patch(target, new, spec, create, spec_set, autospec, new_callable, 
**kwargs)
... 
>>> foo = object()
>>> with my_patch('__main__.foo') as m:
...  pass
... 
>>> m
<MyMock name='foo' id='4299881744'>

Original comment by fuzzyman on 25 Mar 2012 at 3:38

• Changed state: WontFix

[GoogleCodeExporter]

I'm re-opening this issue. I've come round to thinking that patch.DEFAULT_MOCK 
(or similar) isn't an unreasonable feature request. I'm not certain it will get 
into 1.0, but I'm considering it. A patch (no pun intended) with tests and 
documentation would improve its chances. ;-)

Original comment by fuzzyman on 14 Apr 2012 at 10:01

• Changed state: New

[GoogleCodeExporter]

There's a problem here. I tried something similar to this, but got

ValueError: Cannot use 'autospec' and 'new_callable' together

Why is that? I mean, my new_callable is a subclass of MagicMock, it would be 
natural to let it autospec.

Original comment by k...@k-bx.com on 9 May 2012 at 12:08

[GoogleCodeExporter]

The issue is that create_autospec creates the mocks for you, so it would need 
modifying to be able to take a _mock_class argument (or similar) to use 
something other than the standard MagicMock.

Original comment by fuzzyman on 9 May 2012 at 12:29

[GoogleCodeExporter]

Yeah, I think that's that would be the best way (I think it could be 
implemented in terms of DEFAULT_MOCK feature also).

Original comment by k...@k-bx.com on 9 May 2012 at 12:53