Android Crop Center of Bitmap

Несколько решений обсуждаются в http://blog.xelnor.net/python-mocking-datetime/ . В целом:

Mock object - Простой и эффективный, но прерывает проверку isinstance ():

target = datetime.datetime(2009, 1, 1)
with mock.patch.object(datetime, 'datetime', mock.Mock(wraps=datetime.datetime)) as patched:
    patched.now.return_value = target
    print(datetime.datetime.now())

Класс Mock

import datetime
import mock

real_datetime_class = datetime.datetime

def mock_datetime_now(target, dt):
    class DatetimeSubclassMeta(type):
        @classmethod
        def __instancecheck__(mcs, obj):
            return isinstance(obj, real_datetime_class)

    class BaseMockedDatetime(real_datetime_class):
        @classmethod
        def now(cls, tz=None):
            return target.replace(tzinfo=tz)

        @classmethod
        def utcnow(cls):
            return target

    # Python2 & Python3 compatible metaclass
    MockedDatetime = DatetimeSubclassMeta('datetime', (BaseMockedDatetime,), {})

    return mock.patch.object(dt, 'datetime', MockedDatetime)

Использовать как:

with mock_datetime_now(target, datetime):
   ....