contract-testing

name	contract-testing
description	Contract Testing: Consumer-Driven Contract Testing with Pact (REST, messaging, Pact Broker, can-i-deploy), OpenAPI contract testing with Prism mock server and dredd, schema compatibility (ajv, Protobuf wire rules, Avro + Schema Registry), and breaking change detection with oasdiff in CI.

Contract Testing

Test API contracts between services to catch breaking changes before deployment.

When to Activate

• Setting up Pact consumer-driven contract tests for REST or message-based APIs
• Validating OpenAPI specs with Prism mock server or dredd
• Checking schema compatibility (JSON Schema, Protobuf, Avro)
• Detecting breaking changes in CI with oasdiff
• Implementing can-i-deploy gates before deployment
• Establishing a safety net between two independently deployed microservices so either team can release without coordinating manually
• Adding a CI gate that blocks any pull request that introduces a field removal, rename, or type change to a public REST API
• Testing a Kafka event consumer against the exact message schema that the producer publishes, without spinning up the full event pipeline

---

Consumer-Driven Contract Testing (Pact)

 CONSUMER SIDE                    PROVIDER SIDE
┌──────────────┐                 ┌──────────────────┐
│ Consumer Test│ ──Pact File──▶  │ Provider          │
│ (defines     │                 │ Verification Test │
│  expectations│ ◀──Result────── │ (runs against     │
│  on API)     │                 │  real service)    │
└──────────────┘                 └──────────────────┘
        │                                 ▲
        └──────────▶ Pact Broker ─────────┘
                   (stores pacts,
                    tracks versions)

Consumer Test (TypeScript)

// consumer.pact.spec.ts
import { PactV3,  }  ;
 {  }  ;

 { like, eachLike, iso8601DateTime } = ;

 provider =  ({
  : ,
  : ,
  : ,  
  : ,
});

(,  {
  (,  {
    (,  () => {
       provider
        .()  
        .()
        .({
          : ,
          : ,
          : { : () },
        })
        .({
          : ,
          : { :  },
          : {
            : (),
            : (),
            : ({
              : (),
              : (),
              : (),
            }),
            : (),
          },
        })
        .( (mockServer) => {
           client =  (mockServer.);
           order =  client.();

          (order.).();
          (order.).();
        });
    });

    (,  () => {
       provider
        .()
        .()
        .({ : , :  })
        .({
          : ,
          : { : () },
        })
        .( (mockServer) => {
           client =  (mockServer.);
           (client.())..();
        });
    });
  });
});