def document_should_store_fields_in_order(self):
        class Doc(Document):
            three = Mock(Field, _field_counter=3)
            two = Mock(Field, _field_counter=2)
            one = Mock(Field, _field_counter=1)

        doc = Doc()
        self.assertEquals([field._field_counter for field in doc._fields.values()], [1, 2, 3])