Explore comprehensive testing methodologies for AI-driven applications in this 42-minute conference talk from Devoxx. Learn practical strategies for ensuring reliability and maintainability of AI systems that interact with users, tools, and external APIs. Discover how to write effective unit and functional tests specifically designed for AI behaviors, and master robust integration testing techniques including interaction recording and mocking for secure, deterministic validation. Examine how traditional AI testing methods such as evaluation datasets and metric-based validation complement system-level testing approaches. Gain concrete techniques for building test suites that enhance the safety and sustainability of evolving AI systems while maintaining rapid iteration speed, making this essential knowledge for developers transitioning from traditional software testing to AI application validation.