'Ensure that custom QuerySet classes may be used.'

def test_custom_querysets_set_manager_directly(self):

    class CustomQuerySet(QuerySet, ):
        def not_empty(self):
            return (self.count() > 0)
    class CustomQuerySetManager(QuerySetManager, ):
        queryset_class = CustomQuerySet
    class Post(Document, ):
        objects = CustomQuerySetManager()
    Post.drop_collection()
    self.assertTrue(isinstance(Post.objects, CustomQuerySet))
    self.assertFalse(Post.objects.not_empty())
    Post().save()
    self.assertTrue(Post.objects.not_empty())
    Post.drop_collection()
