Contract Testing for Microservices

February 22, 2026

Contract-Test-Design, Pact-Implementation, Schema-Compatibility-Testing, Ci-Test-Integration

Contract-Testing, Pact, Consumer-Driven-Contracts, Schema-Testing, Avro, Protobuf, Api-Testing, Ci-Testing

Pact, Pact-Broker, Schema-Registry, Protobuf, Avro

Contract Testing for Microservices#

Integration tests verify that services work together, but they require all services to be running. In a system with 20 services, running full integration tests is slow, brittle, and blocks deployments. Contract testing solves this by verifying service interactions independently – each service tests against a contract instead of against a live instance of every dependency.

The Problem with Integration and E2E Tests#

A traditional integration test for “order service calls payment service” requires both services running, along with their databases, message brokers, and any other dependencies. Problems:

Schema Evolution and Compatibility

February 22, 2026

Microservices

Intermediate, Advanced

Schema-Evolution-Design, Compatibility-Mode-Selection, Schema-Registry-Operations, Breaking-Change-Detection

Schema-Evolution, Avro, Protobuf, Json-Schema, Schema-Registry, Backwards-Compatibility, Api-Versioning, Confluent

Confluent-Schema-Registry, Apicurio, Avro, Protobuf, Buf

Schema Evolution and Compatibility#

Every service contract changes over time. New fields get added, old fields get removed, types change. In a monolith, you update the schema and redeploy. In microservices, producers and consumers deploy independently. A schema change that breaks consumers causes production failures. Schema evolution rules and tooling exist to prevent this.

Compatibility Modes#

There are four compatibility modes. Understanding them is essential for operating any schema registry.