It depends on your OO language. If you have garbage collection, you can at the very least refrain yourself to use mutable state all over the place, especially

It depends on your OO language. If you have garbage collection, you can at the very least refrain yourself to use mutable state all over the place, especially at interface boundaries. It's not hard: http://loup-vaillant.fr/tutorials/avoid-assignment http://loup-vaillant.fr/tutorials/avoid-assignment