In which phase of iterative design is user testing most critical?

User testing is most critical during each iteration after initial versions are created because this phase allows designers to gather feedback on the evolving product. Iterative design relies on a cyclical process where concepts are developed, tested, and refined based on user interactions and preferences. By conducting user tests at multiple points during development, designers can identify issues, understand user needs, and make informed adjustments to improve the overall experience. This continuous loop of testing and refinement helps ensure that the final product aligns more closely with user expectations and requirements, resulting in a more successful design outcome.

In contrast, testing solely at the beginning or only after the final version limits the opportunity to incorporate user feedback meaningfully. Conducting no testing at all eliminates critical insights that could enhance usability and satisfaction. Thus, regular testing throughout the design iterations is essential for creating an effective and user-friendly product.