Contract Testing in Action

With Pact, PactFlow, and GitHub Actions

Marie Cruz, Lewis Prescott

• Publisher: Manning
• Year: 2025
• Topic: Computer Science
• eBook ISBN:
  9781638356608
• Subtopic: Programming in Java
• Index: Computer Science

Contract testing is a simple, reliable way to make sure that each service and API plays nice with other components so you can deploy independently and safely.

Large, loosely coupled systems have hundreds, even thousands, of interactions—and traditional testing can often struggle to keep up! Enter contract testing. This rapidly growing new approach checks API and service compatibility by verifying it against an agreed contract. No more unexpected integration issues, and no more breaking things in production!

In Contract Testing in Action you’ll learn:

• The core concepts and practices of contract testing
• Testing microservices with Pact
• Consumer-driven and bi-directional testing
• Building a contract testing framework
• Converting API integration tests to contract tests

Contract Testing in Action introduces the practice of contract testing through engaging hands-on examples. You’ll learn how to introduce contract tests for multiple different types of communication, from REST APIs to event-driven architecture. By the end of this practical guide, you’ll be comfortable with advanced contract testing concepts like can-i-deploy, provider states, and webhooks. You’ll even get tips on how to introduce contract testing to your team and other business stakeholders.

About the technology

It’s difficult to test API and event-based services that can be used by many applications simultaneously through a complex network of integrations. Contract testing offers a straightforward solution. API and service compatibility are verified against agreed-upon contracts that each component in the system—and the developers that build them—can understand and respect. This transformative technique helps uncover integration issues early and adds vital transparency to any system.

About the book

Contract Testing in Action makes it easy for your team to adopt contract testing for microservices and other API-centric systems. You’ll start by learning how contract testing fits into the software development lifecycle, and then you’ll explore practical methods to integrate it with your own tech stack and practices. You’ll use leading contract testing tools—including Pact, PactFlow, and GitHub Actions—to build your own contract testing framework, set up consumer-driven contract testing for REST and GraphQL APIs, and integrate it into your CI/CD pipeline.

What's inside

• Testing microservices with Pact
• Consumer-driven and bi-directional contract testing
• Building a contract testing framework
• Converting API integration tests to contract tests

About the reader

For software developers and quality engineers who have worked with Java or JavaScript, and APIs.

About the author

Marie Cruz is a Software Tester with over ten years of experience and also a Developer Advocate at Grafana Labs. Lewis Prescott is a Test Specialist at IBM with over nine years experience in software testing.

Table of contents

• Contract Testing in Action
• copyright
• contents
• foreword
• preface
• acknowledgments
• about this book
• about the authors
• about the cover illustration
• Part 1 Introduction to contract testing
• 1 Introduction to contract testing
• 2 How contract testing fits into wider testing concepts
• 3 A technical overview of contract testing
• Part 2 Consumer-driven contract testing
• 4 Implementing consumer-driven contract testing for web applications
• 5 Implementing consumer-driven contract testing for mobile clients
• 6 Implementing consumer-driven provider contract tests
• 7 Contract testing for GraphQL
• 8 Contract testing for event-driven architecture
• 9 Storing, hosting, and securing the contracts
• 10 Setting up contract testing in a CI/CD pipeline
• Part 3 Provider-driven contract testing
• 11 Implementing provider-driven contract testing
• 12 Moving integration tests to contract tests
• appendix A Tool comparisons
• appendix B Setting up project requirements for consumer contract testing (web applications)
• appendix C Answers to chapter exercises
• index