What is included in the testing phase of the design process?

The testing phase of the design process is centered around obtaining actual feedback from users, making option B the correct choice. This phase involves engaging with real users as they interact with a prototype or product, allowing designers to observe behaviors, collect insights, and understand user experiences firsthand. Such direct interaction is vital for identifying usability issues, understanding user needs, and gathering suggestions for improvements. It ensures that the design meets user expectations and requirements before it's finalized.

Delving into the other options, developing prototypes without real user input does not align with the core objective of testing, which is to validate design assumptions through actual user feedback. Similarly, defining design goals and objectives typically occurs in earlier phases of the design process, not during testing. Finalizing design assets is also a later stage, following the testing phase, where feedback is implemented to refine the design. Thus, interaction with users stands out as the essential aspect of testing in the design process.