CODEWITHSUNDEEP
pythonmocking
Philip Ridout
Philip Ridout

Reputation: 1007

How to Mock a missing attribute

I have a line of code that is:

if not hasattr(class.a, u'c'):
    return

How do I mock out class so that class.a.c returns False for hasattr?

If I do this:

>>> from mock import MagicMock
>>> mock_class = MagicMock(spec=[u'a'])
>>> hasattr(mock_class, u'a')
True
>>> hasattr(mock_class, u'b')
False
>>> hasattr(mock_class.a, u'c')
True

Although I dont spec class.a.c, its being mocked!!!

Upvotes: 17

Views: 7408

Answers (2)

Kyle
Kyle

Reputation: 887

You can delete the attribute, which will cause hasattr to return False.

From the Documentation:

>>> mock = MagicMock()
>>> hasattr(mock, 'm')
True
>>> del mock.m
>>> hasattr(mock, 'm')
False
>>> del mock.f
>>> mock.f
Traceback (most recent call last):
    ...
AttributeError: f

For your specific example, since mock_class.a is another Mock, you can do del mock_class.a.c.

Upvotes: 7

Tomáš Diviš
Tomáš Diviš

Reputation: 1076

Actually mock_class.a will create another MagicMock, which don't have a spec. The only way I can think of is to assign the attribute a of the mock_class with another MagicMock with spec, like this:

mock_class = MagicMock(spec=[u'a'])
mock_class.a = MagicMock(spec=[u'a'])
hasattr(mock_class.a, u'c')  # returns False

Also if you have some real objects you want to mock, there is a possibility to do some recursive autospecing.

Upvotes: 11

Related Questions