The significance of UX/UI testing in product development lies in its ability to ensure that products meet user needs and provide a satisfying experience. Testing involves evaluating user interactions and feedback on interfaces and designs, identifying usability issues, and validating design assumptions. Through methodologies like usability testing and A/B testing, teams can refine products iteratively based on real user data. Prioritizing UX/UI testing leads to higher user satisfaction, increased adoption rates, and ultimately, better product success in the market.