During this phase, you will update the user interface based on the results of testing the prototype. For example, you may revise prototype scripts, add tapered prompts and customizable expertise levels, create dialogs for inter- and intra-application interactions.
Finally, you will want to iterate the Design—Prototype—Test—Refine process. This includes, in the Test phase, users from previous rounds of testing and users new to the system. Ideally, the final usability test should be on a deployed system to allow evaluation of its accuracy, latency, barge-in characteristics and quality of speech output.