Because they were very specific to code. 
After we remove preprocessing, `order_values` will contain raw data, so there are no `ascending?`, `expr.name` and `expr.relation.name`.
I tried swap `node = relation.order_values.first` with `node = relation.arel.orders.first`, but it raise error.
So i decided remove those specs for now.
Please let me know if i need bring them back and adapt to current implementation?