def METHOD_NAME(self, backend):
    obj = models.Book.objects.create(
        title="Test", publication_date=date(2017, 10, 18), number_of_pages=100
    )
    backend().reset_mock()
    obj.title = "Updated test"
    obj.save()
    self.assertEqual(backend().add.call_count, 1)
    indexed_object = backend().add.call_args[0][0]
    self.assertEqual(indexed_object.title, "Updated test")