How to Unit test with different settings in Django?

Is there any simple mechanism for overriding Django settings for a unit test? I have a manager on one of my models that returns a specific number of the latest objects. The number of objects it returns is defined by a NUM_LATEST setting.

This has the potential to make my tests fail if someone were to change the setting. How can I override the settings on setUp() and subsequently restore them on tearDown()? If that isn't possible, is there some way I can monkey patch the method or mock the settings?

EDIT: Here is my manager code:

class LatestManager(models.Manager):
    """
    Returns a specific number of the most recent public Articles as defined by 
    the NEWS_LATEST_MAX setting.
    """
    def get_query_set(self):
        num_latest = getattr(settings, 'NEWS_NUM_LATEST', 10)
        return super(LatestManager, self).get_query_set().filter(is_public=True)[:num_latest]

The manager uses settings.NEWS_LATEST_MAX to slice the queryset. The getattr() is simply used to provide a default should the setting not exist.