def METHOD_NAME(self):
    """Adding/Deleting the last post in a thread should
    update the last_post field
    """
    t = ThreadFactory()
    u = UserFactory()
    # add a new post, then check that last_post is updated
    new_post = t.new_post(creator=u, content="test")
    self.assertEqual(t.last_post.id, new_post.id)
    # delete the new post, then check that last_post is updated
    new_post.delete()
    self.assertIsNone(t.last_post.id)