CI/CD brings tremendous value to development teams. The rapid availability of feedback helps developers make informed decisions about their design choices and lets teams deploy with confidence. But when systems become large and test times go from seconds to hours, how do we get our groove back? In this talk, we’ll explore strategies for validating large, complex systems, such as: - Setting well-defined component boundaries - Flexibly modeling dependencies between these components - Ranking tests by cost versus value - Testing in production with canary launches and feature flags These and similar techniques let us minimize test times, maximize confidence, and free our teams up to focus on delivering value to customers.