Testing large systems with multiple microservices is hard to understand. You need to understand the whole system, all connections, and how the microservices interconnect. With tracing you get a map of everything which makes your whole system easier to understand. I want to showcase traditional test-driven development vs the new observability-driven development. I'll use open-source tools like Tracetest and OpenTelemetry to showcase how to use trace-based testing and enrich integration tests with trace data.