> And if it is a black-box rewrite, then all that tacit knowledge will be lost, This is a thought experiment on how to avoid that tacit knowledge, not how to d

> And if it is a black-box rewrite, then all that tacit knowledge will be lost, This is a thought experiment on how to avoid that tacit knowledge, not how to deal with it. Consider approaching every edit in the same way you'd approach new code: is the function adequately tested, does the function have a single responsibility, is the intent clear, etc.? The idea is that if you do this, then you won't reach the point where you have a 200-line method with tons of hidden business rules. I agree there's probably a better way of framing this. Still, as a thought experiment, it's worth thinking about when you can and/or should do this.