The dynamic that requires companies to clean room, typically comes from some license that comes with the original product. I license you a black box with 3 swi

The dynamic that requires companies to clean room, typically comes from some license that comes with the original product. I license you a black box with 3 switches on it and 3 lights. The license dictates you may not look inside. The clean room implementation is, I right down what the effect of each switch has upon the lights. I then give that specification to an engineer who's never seen the box. They build a copy of the box, based on the spec.