New · Specialised Track

Contract Testing — testing microservice boundaries

In a monolith, integration testing is straightforward. In microservices, you have 12 services talking to each other — and a breaking API change in one can cascade silently until production. Contract testing with PACT solves this by verifying the agreements between services at build time, not at release time.

This track teaches consumer-driven contract testing using PACT. You’ll write consumer contracts in JavaScript/TypeScript, verify them against provider APIs, and integrate the PACT Broker into CI so breaking changes are caught before they merge.

Start with Lesson 1 → Back to Specialised

This track covers

PACT Consumer-Driven Contracts Provider Verification PACT Broker CI Integration Microservices

Who this is for

Senior SDETs and test leads working on microservices architectures. Also valuable for any tester who’s experienced the pain of integration test suites that are slow, flaky, or only catch breaking changes in UAT.

The 3 lessons

From the contract to the CI gate

Lesson 1

Contract Testing Fundamentals

What consumer-driven contract testing is, why it beats integration testing for microservices, and how PACT implements the pattern.

~30 min read · ~65 min with exercises · Contract Testing

Lesson 2

Writing PACT Tests

Write consumer tests in JavaScript, verify them against a provider API in Node.js, and understand the PACT lifecycle end to end.

~30 min read · ~70 min with exercises · Contract Testing

Lesson 3

PACT in CI

Set up a PACT Broker, integrate consumer and provider pipelines in GitHub Actions, and use can-i-deploy to gate releases.

~30 min read · ~75 min with exercises · Contract Testing

Why this track

The problem contract testing solves

Integration tests for microservices have a fundamental problem: they require all the services to be running at the same time. That means a slow test environment, scheduling conflicts between teams, and test failures that are often environmental rather than functional. And they still only catch breaking changes when the system is assembled — which is usually too late to fix cheaply.

Contract testing decouples consumer and provider. The consumer defines what it needs from the provider. The provider verifies it can deliver that, in isolation, using a mock of the consumer. Both sides run in their own CI pipeline, and a central PACT Broker coordinates the verification. A breaking change on the provider side fails the provider’s own build — before anyone else is affected.

This track teaches the full pattern with PACT, the most widely used consumer-driven contract testing framework. Every example uses NZ fintech and banking service patterns.

Other specialised tracks

Specialised