How would you answer an interview scenario involving testability?

For an interview scenario involving testability, I would first clarify the business goal, scale, constraints, and the failure or quality attribute the interviewer wants to explore. Clean Architecture improves testability by allowing core rules and use cases to run without booting databases, web servers, or external services. For production, test domain behavior directly, mock only true boundaries, and complement unit tests with integration and end-to-end coverage. I would then explain the main alternatives and tradeoffs, identify likely failure modes, and describe how I would validate the solution through testing, observability, security controls, and recovery or rollback planning.