Final answer:
When testing a prototype, you should not tell users which button to press. Instead, observe their natural interactions and gather unbiased feedback to ensure product functionality and design quality meets user needs and specified criteria.
Step-by-step explanation:
As a user is testing your prototype, you should not tell them which button to press. This question addresses the best practices during usability testing of a prototype within the design and development phase. When conducting tests, the facilitator should avoid leading the user and instead observe natural interactions with the prototype. It is important to ask them what they're thinking and have them explain their actions, as it allows the user to provide valuable feedback. An overview of the product could be appropriate as long as it does not influence the users' actions during testing. Comprehensive evaluation of a prototype is crucial; it ensures that design quality is maintained and that the product functionality aligns with user expectations and the specified constraints and criteria.