One question I always ask during a product requirements review to ensure testability is: "How will we measure success for this feature, and what specific criteria will we use to determine if it has been successfully implemented?" This question is crucial because it directly ties the product's functionality to measurable outcomes, ensuring that the team has clear, testable criteria to verify that the feature works as intended. Without clear success metrics, testing can become subjective or inconsistent, leading to unclear results. This question helps identify key performance indicators (KPIs), edge cases, and expected behaviors early on, making it easier to design tests that will validate whether the feature truly meets user needs and requirements. It also aligns development and testing teams on what "done" looks like, avoiding ambiguity and improving the overall quality assurance process.