Can anyone tell me why this isn’t working?
>>> import mock >>> @mock.patch('datetime.date.today') ... def today(cls): ... return date(2010, 1, 1) ... >>> from datetime import date >>> date.today() datetime.date(2010, 12, 19)
Perhaps someone could suggest a better way?
There are a few problems.
First of all, the way you’re using
mock.patch isn’t quite right. When used as a decorator, it replaces the given function/class (in this case,
datetime.date.today) with a
Mock object only within the decorated function. So, only within your
datetime.date.today be a different function, which doesn’t appear to be what you want.
What you really want seems to be more like this:
@mock.patch('datetime.date.today') def test(): datetime.date.today.return_value = date(2010, 1, 1) print datetime.date.today()
Unfortunately, this won’t work:
>>> test() Traceback (most recent call last): File "<stdin>", line 1, in <module> File "build/bdist.macosx-10.6-universal/egg/mock.py", line 557, in patched File "build/bdist.macosx-10.6-universal/egg/mock.py", line 620, in __enter__ TypeError: can't set attributes of built-in/extension type 'datetime.date'
This fails because Python built-in types are immutable – see this answer for more details.
In this case, I would subclass datetime.date myself and create the right function:
import datetime class NewDate(datetime.date): @classmethod def today(cls): return cls(2010, 1, 1) datetime.date = NewDate
And now you could do:
>>> datetime.date.today() NewDate(2010, 1, 1)