How do you design a testing strategy for microservices architecture at scale?

By combining unit, contract, integration, and end-to-end tests with service isolation.

Microservices require a layered testing strategy because services are independently deployable. Unit tests validate internal logic, contract tests ensure API compatibility, integration tests verify service interactions, and end-to-end tests validate business flows. A key principle is avoiding over-reliance on full system tests due to cost and flakiness.