'Ensure that the list fields can be updated using the positional
operator.'

def test_update_using_positional_operator(self):

    class Comment(EmbeddedDocument, ):
        by = StringField()
        votes = IntField()
    class BlogPost(Document, ):
        title = StringField()
        comments = ListField(EmbeddedDocumentField(Comment))
    BlogPost.drop_collection()
    c1 = Comment(by='joe', votes=3)
    c2 = Comment(by='jane', votes=7)
    BlogPost(title='ABC', comments=[c1, c2]).save()
    BlogPost.objects(comments__by='jane').update(inc__comments__S__votes=1)
    post = BlogPost.objects.first()
    self.assertEqual(post.comments[1].by, 'jane')
    self.assertEqual(post.comments[1].votes, 8)
