django-testing: mock datetime.datetime.now()

tests.py

import mock
from django.test import TestCase, Client

import datetime
class StubDate(datetime.datetime):
    pass

class TestApp(TestCase):

    @mock.patch('app.views.datetime.datetime', StubDate) #app is the $django_application_name
    def test_now(self):
        from datetime import datetime
        StubDate.now = classmethod(lambda cls: datetime(2015, 03, 11, 00, 16, 31, 99))

        response = self.client.get('/holiday/')
        self.assertEqual(response.status_code, 200)
        print response.content
        self.assertContains(response, '2015-03-11 00:16:31.000099')

views.py

import datetime
from django.http import HttpResponse

def now():
    return datetime.datetime.now()

def index(request):
    return HttpResponse(now())

My test code worked. OK, let me try to update it based on your feedback.