What is usability testing? Usability testing calls for representative users to perform representative tasks as a means to reveal the interactive strengths and opportunities for improvement of a device. You can think of the activity as pressure testing or debugging the user interface of a device in terms of how it serves the users’ needs, a critical need being safe operation. Tests may focus on early design concept models, more advanced prototypes, and even production units. A two-person team usually collaborates to run test sessions with one participant at a time. Good practice calls for preparing a detailed usability test plan and report that can be added to the design history file of a device.