Contract Testing in Kotlin: A Step-by-Step Workshop with Pact and Spring Cloud Contract

What We're Building By the end of this workshop, you'll have a working consumer-driven contract test suite in Kotlin. You'll know how to write a consumer contract with Pact, verify it on the provider side, and wire it into your CI pipeline so broken API changes never reach production again. Let me show you a pattern I use in every project with more than two services talking to each other. Prerequisites Kotlin project with Gradle JUnit 5 Familiarity with Spring Boot (helpful, not required) A service that calls another service over HTTP Add these to your build.gradle.kts : testImplementation ( "au.com.dius.pact.consumer:junit5:4.6.5" ) testImplementation ( "au.com.dius.pact.provider:junit5spring:4.6.5" ) Step 1: Write the Consumer Contract The consumer defines what it expects. This is the key insight — the service calling the API describes exactly which fields it depends on. @ExtendWith ( PactConsumerTestExt :: class ) @PactTestFor ( providerName = "order-service" , port = "8080" ) class