contract-testing

name	contract-testing
description	Consumer-driven contract testing with Pact, schema validation, and API compatibility verification.
layer	domain
category	testing
triggers	["contract test","pact","consumer driven","api contract","schema validation"]
inputs	["API contract testing requirements","Consumer-driven testing setup","Schema validation strategies","API compatibility verification"]
outputs	["Pact consumer and provider tests","Schema validation configurations","Contract verification workflows","CI/CD integration for contract tests"]
linksTo	["api-testing","testing-patterns","openapi","microservices"]
linkedFrom	[]
preferredNextSkills	["api-testing","testing-patterns","microservices"]
fallbackSkills	["openapi"]
riskLevel	low
memoryReadPolicy	selective
memoryWritePolicy	none
sideEffects	[]

Consumer-Driven Contract Testing

Purpose

Provide expert guidance on consumer-driven contract testing (CDCT) with Pact, schema validation with Zod/JSON Schema, API compatibility verification, and CI integration. Ensures APIs evolve without breaking consumers in microservice architectures.

Why Contract Testing

┌────────────────────────────────────────────────┐
│           Testing Pyramid for APIs             │
│                                                │
│              ┌──────────┐                      │
│              │  E2E     │  Slow, brittle       │
│            ┌─┴──────────┴─┐                    │
│            │  Integration  │  Needs live deps   │
│          ┌─┴──────────────┴─┐                  │
│          │  Contract Tests   │  Fast, isolated  │  ← This skill
│        ┌─┴──────────────────┴─┐                │
│        │     Unit Tests        │                │
│        └───────────────────────┘                │
└────────────────────────────────────────────────┘

Contract tests verify that a provider API meets the expectations of its consumers without requiring both services to be running simultaneously.

Pact Consumer Test (TypeScript)

The consumer defines what it expects from the provider:

// consumer/tests/user-service.pact.test.ts
import { PactV4, MatchersV3 } from '@pact-foundation/pact';
import { UserApiClient } from '../src/user-api-client';

const { like, eachLike, string, integer, datetime } = MatchersV3;

const provider = new PactV4({
  consumer: 'OrderService',
  provider: 'UserService',
  dir: './pacts', // output directory for contract files
});

describe('User Service API', () => {
  (,  {
    (,  () => {
       provider
        .()
        .()
        .()
        .(, ,  {
          builder.({ :  });
        })
        .(,  {
          builder
            .({ :  })
            .({
              : (),
              : (),
              : (),
              : (, ),
              : ({
                : (),
                : (),
              }),
            });
        })
        .( (mockServer) => {
           client =  (mockServer.);
           user =  client.();

          (user.).();
          (user.).();
          (user.).();
        });
    });

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

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