Plus one for deterministic software. It's an incredibly useful property when you want to test something. Particularly when doing major version upgrades and when

Plus one for deterministic software. It's an incredibly useful property when you want to test something. Particularly when doing major version upgrades and when replacing entire systems. Unfortunately strict determinism and test coverage often go hand in hand. Either the developer gets it or (s)he doesn't. Fortunately you often do get a least a moderate level of determinism even from the most awful software.