What I would advise system designers is twofold:
1. focus on the distinction between the practical function and aesthetic function in product features, and try not to conflate the two
2. seek to produce order rather than chaos, recalling that the definition of order in physics is when a given event or phenomenon can only be achieved in one way (for example, don’t have two tabs on the same web page that do the same thing)
Product testing is a giant can of worms. Few in the market-driven community do this extensively.