Testing Microservices

Imagine you're building an e-commerce application using microservices. Your application consists of several independently deployed services:

Each service has its own business logic, APIs, database, and dependencies.

Now suppose your team changes the Payment Service to support a new payment provider. You run the unit tests, and everything passes. But after deploying the change, customers start experiencing checkout failures.

The problem isn't necessarily in the Payment Service's business logic. Perhaps it changed an API response that the Order Service depends on, or introduced a timeout that causes requests to fail. This illustrates one of the biggest challenges of testing microservices.

A service can work correctly in isolation while the overall system still fails.

Testing microservices requires validating individual components, interactions between services, and complete business workflows. The goal is to catch problems early without building a test suite that takes hours to execute or breaks whenever an unrelated service changes.