In product design. A designer will design a high-quality product, which is clearly defined and consider about usability of the user. Therefore, the designer's decisions must be made with prudence, and foresight. Such as production application is designed for user trials. Use the domain from the real users of components.
designer create a application then send application to some user to try and then designer got feedback and designer develop application and send to user again, Designer do it Until them sure application without error.