# Contract Testing Essentials (Pact)

## Principle

Contract testing validates API contracts between consumer and provider services without requiring integrated end-to-end tests. Store consumer contracts alongside integration specs, version contracts semantically, and publish on every CI run. Provider verification before merge surfaces breaking changes immediately, while explicit fallback behavior (timeouts, retries, error payloads) captures resilience guarantees in contracts.

## Rationale

Traditional integration testing requires running both consumer and provider simultaneously, creating slow, flaky tests with complex setup. Contract testing decouples services: consumers define expectations (pact files), providers verify against those expectations independently. This enables parallel development, catches breaking changes early, and documents API behavior as executable specifications. Pair contract tests with API smoke tests to validate data mapping and UI rendering in tandem.

## Pattern Examples

### Example 1: Pact Consumer Test (Frontend → Backend API)

**Context**: React application consuming a user management API, defining expected interactions.

**Implementation**:

```typescript
// tests/contract/user-api.pact.spec.ts
import { PactV3, MatchersV3 } from '@pact-foundation/pact';
import { getUserById, createUser, User } from '@/api/user-service';

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

/**
 * Consumer-Driven Contract Test
 * - Consumer (React app) defines expected API behavior
 * - Generates pact file for provider to verify
 * - Runs in isolation (no real backend required)
 */

const provider = new PactV3({
  consumer: 'user-management-web',
  provider: 'user-api-service',
  dir: './pacts', // Output directory for pact files
  logLevel: 'warn',
});

describe('User API Contract', () => {
  describe('GET /users/:id', () => {
    it('should return user when user exists', async () => {
      // Arrange: Define expected interaction
      await provider
        .given('user with id 1 exists') // Provider state
        .uponReceiving('a request for user 1')
        .withRequest({
          method: 'GET',
          path: '/users/1',
          headers: {
            Accept: 'application/json',
            Authorization: like('Bearer token123'), // Matcher: any string
          },
        })
        .willRespondWith({
          status: 200,
          headers: {
            'Content-Type': 'application/json',
          },
          body: like({
            id: integer(1),
            name: string('John Doe'),
            email: string('john@example.com'),
            role: string('user'),
            createdAt: string('2025-01-15T10:00:00Z'),
          }),
        })
        .executeTest(async (mockServer) => {
          // Act: Call consumer code against mock server
          const user = await getUserById(1, {
            baseURL: mockServer.url,
            headers: { Authorization: 'Bearer token123' },
          });

          // Assert: Validate consumer behavior
          expect(user).toEqual(
            expect.objectContaining({
              id: 1,
              name: 'John Doe',
              email: 'john@example.com',
              role: 'user',
            }),
          );
        });
    });

    it('should handle 404 when user does not exist', async () => {
      await provider
        .given('user with id 999 does not exist')
        .uponReceiving('a request for non-existent user')
        .withRequest({
          method: 'GET',
          path: '/users/999',
          headers: { Accept: 'application/json' },
        })
        .willRespondWith({
          status: 404,
          headers: { 'Content-Type': 'application/json' },
          body: {
            error: 'User not found',
            code: 'USER_NOT_FOUND',
          },
        })
        .executeTest(async (mockServer) => {
          // Act & Assert: Consumer handles 404 gracefully
          await expect(getUserById(999, { baseURL: mockServer.url })).rejects.toThrow('User not found');
        });
    });
  });

  describe('POST /users', () => {
    it('should create user and return 201', async () => {
      const newUser: Omit<User, 'id' | 'createdAt'> = {
        name: 'Jane Smith',
        email: 'jane@example.com',
        role: 'admin',
      };

      await provider
        .given('no users exist')
        .uponReceiving('a request to create a user')
        .withRequest({
          method: 'POST',
          path: '/users',
          headers: {
            'Content-Type': 'application/json',
            Accept: 'application/json',
          },
          body: like(newUser),
        })
        .willRespondWith({
          status: 201,
          headers: { 'Content-Type': 'application/json' },
          body: like({
            id: integer(2),
            name: string('Jane Smith'),
            email: string('jane@example.com'),
            role: string('admin'),
            createdAt: string('2025-01-15T11:00:00Z'),
          }),
        })
        .executeTest(async (mockServer) => {
          const createdUser = await createUser(newUser, {
            baseURL: mockServer.url,
          });

          expect(createdUser).toEqual(
            expect.objectContaining({
              id: expect.any(Number),
              name: 'Jane Smith',
              email: 'jane@example.com',
              role: 'admin',
            }),
          );
        });
    });
  });
});
```

**package.json scripts**:

```json
{
  "scripts": {
    "test:contract": "jest tests/contract --testTimeout=30000",
    "pact:publish": "pact-broker publish ./pacts --consumer-app-version=$GIT_SHA --broker-base-url=$PACT_BROKER_URL --broker-token=$PACT_BROKER_TOKEN"
  }
}
```

**Key Points**:

- **Consumer-driven**: Frontend defines expectations, not backend
- **Matchers**: `like`, `string`, `integer` for flexible matching
- **Provider states**: given() sets up test preconditions
- **Isolation**: No real backend needed, runs fast
- **Pact generation**: Automatically creates JSON pact files

---

### Example 2: Pact Provider Verification (Backend validates contracts)

**Context**: Node.js/Express API verifying pacts published by consumers.

**Implementation**:

```typescript
// tests/contract/user-api.provider.spec.ts
import { Verifier, VerifierOptions } from '@pact-foundation/pact';
import { server } from '../../src/server'; // Your Express/Fastify app
import { seedDatabase, resetDatabase } from '../support/db-helpers';

/**
 * Provider Verification Test
 * - Provider (backend API) verifies against published pacts
 * - State handlers setup test data for each interaction
 * - Runs before merge to catch breaking changes
 */

describe('Pact Provider Verification', () => {
  let serverInstance;
  const PORT = 3001;

  beforeAll(async () => {
    // Start provider server
    serverInstance = server.listen(PORT);
    console.log(`Provider server running on port ${PORT}`);
  });

  afterAll(async () => {
    // Cleanup
    await serverInstance.close();
  });

  it('should verify pacts from all consumers', async () => {
    const opts: VerifierOptions = {
      // Provider details
      provider: 'user-api-service',
      providerBaseUrl: `http://localhost:${PORT}`,

      // Pact Broker configuration
      pactBrokerUrl: process.env.PACT_BROKER_URL,
      pactBrokerToken: process.env.PACT_BROKER_TOKEN,
      publishVerificationResult: process.env.CI === 'true',
      providerVersion: process.env.GIT_SHA || 'dev',

      // State handlers: Setup provider state for each interaction
      stateHandlers: {
        'user with id 1 exists': async () => {
          await seedDatabase({
            users: [
              {
                id: 1,
                name: 'John Doe',
                email: 'john@example.com',
                role: 'user',
                createdAt: '2025-01-15T10:00:00Z',
              },
            ],
          });
          return 'User seeded successfully';
        },

        'user with id 999 does not exist': async () => {
          // Ensure user doesn't exist
          await resetDatabase();
          return 'Database reset';
        },

        'no users exist': async () => {
          await resetDatabase();
          return 'Database empty';
        },
      },

      // Request filters: Add auth headers to all requests
      requestFilter: (req, res, next) => {
        // Mock authentication for verification
        req.headers['x-user-id'] = 'test-user';
        req.headers['authorization'] = 'Bearer valid-test-token';
        next();
      },

      // Timeout for verification
      timeout: 30000,
    };

    // Run verification
    await new Verifier(opts).verifyProvider();
  });
});
```

**CI integration**:

```yaml
# .github/workflows/pact-provider.yml
name: Pact Provider Verification
on:
  pull_request:
  push:
    branches: [main]

jobs:
  verify-contracts:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version-file: '.nvmrc'

      - name: Install dependencies
        run: npm ci

      - name: Start database
        run: docker-compose up -d postgres

      - name: Run migrations
        run: npm run db:migrate

      - name: Verify pacts
        run: npm run test:contract:provider
        env:
          PACT_BROKER_URL: ${{ secrets.PACT_BROKER_URL }}
          PACT_BROKER_TOKEN: ${{ secrets.PACT_BROKER_TOKEN }}
          GIT_SHA: ${{ github.sha }}
          CI: true

      - name: Can I Deploy?
        run: |
          npx pact-broker can-i-deploy \
            --pacticipant user-api-service \
            --version ${{ github.sha }} \
            --to-environment production
        env:
          PACT_BROKER_BASE_URL: ${{ secrets.PACT_BROKER_URL }}
          PACT_BROKER_TOKEN: ${{ secrets.PACT_BROKER_TOKEN }}
```

**Key Points**:

- **State handlers**: Setup provider data for each given() state
- **Request filters**: Add auth/headers for verification requests
- **CI publishing**: Verification results sent to broker
- **can-i-deploy**: Safety check before production deployment
- **Database isolation**: Reset between state handlers

---

### Example 3: Contract CI Integration (Consumer & Provider Workflow)

**Context**: Complete CI/CD workflow coordinating consumer pact publishing and provider verification.

**Implementation**:

```yaml
# .github/workflows/pact-consumer.yml (Consumer side)
name: Pact Consumer Tests
on:
  pull_request:
  push:
    branches: [main]

jobs:
  consumer-tests:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version-file: '.nvmrc'

      - name: Install dependencies
        run: npm ci

      - name: Run consumer contract tests
        run: npm run test:contract

      - name: Publish pacts to broker
        if: github.ref == 'refs/heads/main' || github.event_name == 'pull_request'
        run: |
          npx pact-broker publish ./pacts \
            --consumer-app-version ${{ github.sha }} \
            --branch ${{ github.head_ref || github.ref_name }} \
            --broker-base-url ${{ secrets.PACT_BROKER_URL }} \
            --broker-token ${{ secrets.PACT_BROKER_TOKEN }}

      - name: Tag pact with environment (main branch only)
        if: github.ref == 'refs/heads/main'
        run: |
          npx pact-broker create-version-tag \
            --pacticipant user-management-web \
            --version ${{ github.sha }} \
            --tag production \
            --broker-base-url ${{ secrets.PACT_BROKER_URL }} \
            --broker-token ${{ secrets.PACT_BROKER_TOKEN }}
```

```yaml
# .github/workflows/pact-provider.yml (Provider side)
name: Pact Provider Verification
on:
  pull_request:
  push:
    branches: [main]
  repository_dispatch:
    types: [pact_changed] # Webhook from Pact Broker

jobs:
  verify-contracts:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version-file: '.nvmrc'

      - name: Install dependencies
        run: npm ci

      - name: Start dependencies
        run: docker-compose up -d

      - name: Run provider verification
        run: npm run test:contract:provider
        env:
          PACT_BROKER_URL: ${{ secrets.PACT_BROKER_URL }}
          PACT_BROKER_TOKEN: ${{ secrets.PACT_BROKER_TOKEN }}
          GIT_SHA: ${{ github.sha }}
          CI: true

      - name: Publish verification results
        if: always()
        run: echo "Verification results published to broker"

      - name: Can I Deploy to Production?
        if: github.ref == 'refs/heads/main'
        run: |
          npx pact-broker can-i-deploy \
            --pacticipant user-api-service \
            --version ${{ github.sha }} \
            --to-environment production \
            --broker-base-url ${{ secrets.PACT_BROKER_URL }} \
            --broker-token ${{ secrets.PACT_BROKER_TOKEN }} \
            --retry-while-unknown 6 \
            --retry-interval 10

      - name: Record deployment (if can-i-deploy passed)
        if: success() && github.ref == 'refs/heads/main'
        run: |
          npx pact-broker record-deployment \
            --pacticipant user-api-service \
            --version ${{ github.sha }} \
            --environment production \
            --broker-base-url ${{ secrets.PACT_BROKER_URL }} \
            --broker-token ${{ secrets.PACT_BROKER_TOKEN }}
```

**Pact Broker Webhook Configuration**:

```json
{
  "events": [
    {
      "name": "contract_content_changed"
    }
  ],
  "request": {
    "method": "POST",
    "url": "https://api.github.com/repos/your-org/user-api/dispatches",
    "headers": {
      "Authorization": "Bearer ${user.githubToken}",
      "Content-Type": "application/json",
      "Accept": "application/vnd.github.v3+json"
    },
    "body": {
      "event_type": "pact_changed",
      "client_payload": {
        "pact_url": "${pactbroker.pactUrl}",
        "consumer": "${pactbroker.consumerName}",
        "provider": "${pactbroker.providerName}"
      }
    }
  }
}
```

**Key Points**:

- **Automatic trigger**: Consumer pact changes trigger provider verification via webhook
- **Branch tracking**: Pacts published per branch for feature testing
- **can-i-deploy**: Safety gate before production deployment
- **Record deployment**: Track which version is in each environment
- **Parallel dev**: Consumer and provider teams work independently

---

### Example 4: Resilience Coverage (Testing Fallback Behavior)

**Context**: Capture timeout, retry, and error handling behavior explicitly in contracts.

**Implementation**:

```typescript
// tests/contract/user-api-resilience.pact.spec.ts
import { PactV3, MatchersV3 } from '@pact-foundation/pact';
import { getUserById, ApiError } from '@/api/user-service';

const { like, string } = MatchersV3;

const provider = new PactV3({
  consumer: 'user-management-web',
  provider: 'user-api-service',
  dir: './pacts',
});

describe('User API Resilience Contract', () => {
  /**
   * Test 500 error handling
   * Verifies consumer handles server errors gracefully
   */
  it('should handle 500 errors with retry logic', async () => {
    await provider
      .given('server is experiencing errors')
      .uponReceiving('a request that returns 500')
      .withRequest({
        method: 'GET',
        path: '/users/1',
        headers: { Accept: 'application/json' },
      })
      .willRespondWith({
        status: 500,
        headers: { 'Content-Type': 'application/json' },
        body: {
          error: 'Internal server error',
          code: 'INTERNAL_ERROR',
          retryable: true,
        },
      })
      .executeTest(async (mockServer) => {
        // Consumer should retry on 500
        try {
          await getUserById(1, {
            baseURL: mockServer.url,
            retries: 3,
            retryDelay: 100,
          });
          fail('Should have thrown error after retries');
        } catch (error) {
          expect(error).toBeInstanceOf(ApiError);
          expect((error as ApiError).code).toBe('INTERNAL_ERROR');
          expect((error as ApiError).retryable).toBe(true);
        }
      });
  });

  /**
   * Test 429 rate limiting
   * Verifies consumer respects rate limits
   */
  it('should handle 429 rate limit with backoff', async () => {
    await provider
      .given('rate limit exceeded for user')
      .uponReceiving('a request that is rate limited')
      .withRequest({
        method: 'GET',
        path: '/users/1',
      })
      .willRespondWith({
        status: 429,
        headers: {
          'Content-Type': 'application/json',
          'Retry-After': '60', // Retry after 60 seconds
        },
        body: {
          error: 'Too many requests',
          code: 'RATE_LIMIT_EXCEEDED',
        },
      })
      .executeTest(async (mockServer) => {
        try {
          await getUserById(1, {
            baseURL: mockServer.url,
            respectRateLimit: true,
          });
          fail('Should have thrown rate limit error');
        } catch (error) {
          expect(error).toBeInstanceOf(ApiError);
          expect((error as ApiError).code).toBe('RATE_LIMIT_EXCEEDED');
          expect((error as ApiError).retryAfter).toBe(60);
        }
      });
  });

  /**
   * Test timeout handling
   * Verifies consumer has appropriate timeout configuration
   */
  it('should timeout after 10 seconds', async () => {
    await provider
      .given('server is slow to respond')
      .uponReceiving('a request that times out')
      .withRequest({
        method: 'GET',
        path: '/users/1',
      })
      .willRespondWith({
        status: 200,
        headers: { 'Content-Type': 'application/json' },
        body: like({ id: 1, name: 'John' }),
      })
      .withDelay(15000) // Simulate 15 second delay
      .executeTest(async (mockServer) => {
        try {
          await getUserById(1, {
            baseURL: mockServer.url,
            timeout: 10000, // 10 second timeout
          });
          fail('Should have timed out');
        } catch (error) {
          expect(error).toBeInstanceOf(ApiError);
          expect((error as ApiError).code).toBe('TIMEOUT');
        }
      });
  });

  /**
   * Test partial response (optional fields)
   * Verifies consumer handles missing optional data
   */
  it('should handle response with missing optional fields', async () => {
    await provider
      .given('user exists with minimal data')
      .uponReceiving('a request for user with partial data')
      .withRequest({
        method: 'GET',
        path: '/users/1',
      })
      .willRespondWith({
        status: 200,
        headers: { 'Content-Type': 'application/json' },
        body: {
          id: integer(1),
          name: string('John Doe'),
          email: string('john@example.com'),
          // role, createdAt, etc. omitted (optional fields)
        },
      })
      .executeTest(async (mockServer) => {
        const user = await getUserById(1, { baseURL: mockServer.url });

        // Consumer handles missing optional fields gracefully
        expect(user.id).toBe(1);
        expect(user.name).toBe('John Doe');
        expect(user.role).toBeUndefined(); // Optional field
        expect(user.createdAt).toBeUndefined(); // Optional field
      });
  });
});
```

**API client with retry logic**:

```typescript
// src/api/user-service.ts
import axios, { AxiosInstance, AxiosRequestConfig } from 'axios';

export class ApiError extends Error {
  constructor(
    message: string,
    public code: string,
    public retryable: boolean = false,
    public retryAfter?: number,
  ) {
    super(message);
  }
}

/**
 * User API client with retry and error handling
 */
export async function getUserById(
  id: number,
  config?: AxiosRequestConfig & { retries?: number; retryDelay?: number; respectRateLimit?: boolean },
): Promise<User> {
  const { retries = 3, retryDelay = 1000, respectRateLimit = true, ...axiosConfig } = config || {};

  let lastError: Error;

  for (let attempt = 1; attempt <= retries; attempt++) {
    try {
      const response = await axios.get(`/users/${id}`, axiosConfig);
      return response.data;
    } catch (error: any) {
      lastError = error;

      // Handle rate limiting
      if (error.response?.status === 429) {
        const retryAfter = parseInt(error.response.headers['retry-after'] || '60');
        throw new ApiError('Too many requests', 'RATE_LIMIT_EXCEEDED', false, retryAfter);
      }

      // Retry on 500 errors
      if (error.response?.status === 500 && attempt < retries) {
        await new Promise((resolve) => setTimeout(resolve, retryDelay * attempt));
        continue;
      }

      // Handle 404
      if (error.response?.status === 404) {
        throw new ApiError('User not found', 'USER_NOT_FOUND', false);
      }

      // Handle timeout
      if (error.code === 'ECONNABORTED') {
        throw new ApiError('Request timeout', 'TIMEOUT', true);
      }

      break;
    }
  }

  throw new ApiError('Request failed after retries', 'INTERNAL_ERROR', true);
}
```

**Key Points**:

- **Resilience contracts**: Timeouts, retries, errors explicitly tested
- **State handlers**: Provider sets up each test scenario
- **Error handling**: Consumer validates graceful degradation
- **Retry logic**: Exponential backoff tested
- **Optional fields**: Consumer handles partial responses

---

### Example 4: Pact Broker Housekeeping & Lifecycle Management

**Context**: Automated broker maintenance to prevent contract sprawl and noise.

**Implementation**:

```typescript
// scripts/pact-broker-housekeeping.ts
/**
 * Pact Broker Housekeeping Script
 * - Archive superseded contracts
 * - Expire unused pacts
 * - Tag releases for environment tracking
 */

import { execSync } from 'child_process';

const PACT_BROKER_URL = process.env.PACT_BROKER_URL!;
const PACT_BROKER_TOKEN = process.env.PACT_BROKER_TOKEN!;
const PACTICIPANT = 'user-api-service';

/**
 * Tag release with environment
 */
function tagRelease(version: string, environment: 'staging' | 'production') {
  console.log(`🏷️  Tagging ${PACTICIPANT} v${version} as ${environment}`);

  execSync(
    `npx pact-broker create-version-tag \
      --pacticipant ${PACTICIPANT} \
      --version ${version} \
      --tag ${environment} \
      --broker-base-url ${PACT_BROKER_URL} \
      --broker-token ${PACT_BROKER_TOKEN}`,
    { stdio: 'inherit' },
  );
}

/**
 * Record deployment to environment
 */
function recordDeployment(version: string, environment: 'staging' | 'production') {
  console.log(`📝 Recording deployment of ${PACTICIPANT} v${version} to ${environment}`);

  execSync(
    `npx pact-broker record-deployment \
      --pacticipant ${PACTICIPANT} \
      --version ${version} \
      --environment ${environment} \
      --broker-base-url ${PACT_BROKER_URL} \
      --broker-token ${PACT_BROKER_TOKEN}`,
    { stdio: 'inherit' },
  );
}

/**
 * Clean up old pact versions (retention policy)
 * Keep: last 30 days, all production tags, latest from each branch
 */
function cleanupOldPacts() {
  console.log(`🧹 Cleaning up old pacts for ${PACTICIPANT}`);

  execSync(
    `npx pact-broker clean \
      --pacticipant ${PACTICIPANT} \
      --broker-base-url ${PACT_BROKER_URL} \
      --broker-token ${PACT_BROKER_TOKEN} \
      --keep-latest-for-branch 1 \
      --keep-min-age 30`,
    { stdio: 'inherit' },
  );
}

/**
 * Check deployment compatibility
 */
function canIDeploy(version: string, toEnvironment: string): boolean {
  console.log(`🔍 Checking if ${PACTICIPANT} v${version} can deploy to ${toEnvironment}`);

  try {
    execSync(
      `npx pact-broker can-i-deploy \
        --pacticipant ${PACTICIPANT} \
        --version ${version} \
        --to-environment ${toEnvironment} \
        --broker-base-url ${PACT_BROKER_URL} \
        --broker-token ${PACT_BROKER_TOKEN} \
        --retry-while-unknown 6 \
        --retry-interval 10`,
      { stdio: 'inherit' },
    );
    return true;
  } catch (error) {
    console.error(`❌ Cannot deploy to ${toEnvironment}`);
    return false;
  }
}

/**
 * Main housekeeping workflow
 */
async function main() {
  const command = process.argv[2];
  const version = process.argv[3];
  const environment = process.argv[4] as 'staging' | 'production';

  switch (command) {
    case 'tag-release':
      tagRelease(version, environment);
      break;

    case 'record-deployment':
      recordDeployment(version, environment);
      break;

    case 'can-i-deploy':
      const canDeploy = canIDeploy(version, environment);
      process.exit(canDeploy ? 0 : 1);

    case 'cleanup':
      cleanupOldPacts();
      break;

    default:
      console.error('Unknown command. Use: tag-release | record-deployment | can-i-deploy | cleanup');
      process.exit(1);
  }
}

main();
```

**package.json scripts**:

```json
{
  "scripts": {
    "pact:tag": "ts-node scripts/pact-broker-housekeeping.ts tag-release",
    "pact:record": "ts-node scripts/pact-broker-housekeeping.ts record-deployment",
    "pact:can-deploy": "ts-node scripts/pact-broker-housekeeping.ts can-i-deploy",
    "pact:cleanup": "ts-node scripts/pact-broker-housekeeping.ts cleanup"
  }
}
```

**Deployment workflow integration**:

```yaml
# .github/workflows/deploy-production.yml
name: Deploy to Production
on:
  push:
    tags:
      - 'v*'

jobs:
  verify-contracts:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Check pact compatibility
        run: npm run pact:can-deploy ${{ github.ref_name }} production
        env:
          PACT_BROKER_URL: ${{ secrets.PACT_BROKER_URL }}
          PACT_BROKER_TOKEN: ${{ secrets.PACT_BROKER_TOKEN }}

  deploy:
    needs: verify-contracts
    runs-on: ubuntu-latest
    steps:
      - name: Deploy to production
        run: ./scripts/deploy.sh production

      - name: Record deployment in Pact Broker
        run: npm run pact:record ${{ github.ref_name }} production
        env:
          PACT_BROKER_URL: ${{ secrets.PACT_BROKER_URL }}
          PACT_BROKER_TOKEN: ${{ secrets.PACT_BROKER_TOKEN }}
```

**Scheduled cleanup**:

```yaml
# .github/workflows/pact-housekeeping.yml
name: Pact Broker Housekeeping
on:
  schedule:
    - cron: '0 2 * * 0' # Weekly on Sunday at 2 AM

jobs:
  cleanup:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Cleanup old pacts
        run: npm run pact:cleanup
        env:
          PACT_BROKER_URL: ${{ secrets.PACT_BROKER_URL }}
          PACT_BROKER_TOKEN: ${{ secrets.PACT_BROKER_TOKEN }}
```

**Key Points**:

- **Automated tagging**: Releases tagged with environment
- **Deployment tracking**: Broker knows which version is where
- **Safety gate**: can-i-deploy blocks incompatible deployments
- **Retention policy**: Keep recent, production, and branch-latest pacts
- **Webhook triggers**: Provider verification runs on consumer changes

---

## Contract Testing Checklist

Before implementing contract testing, verify:

- [ ] **Pact Broker setup**: Hosted (Pactflow) or self-hosted broker configured
- [ ] **Consumer tests**: Generate pacts in CI, publish to broker on merge
- [ ] **Provider verification**: Runs on PR, verifies all consumer pacts
- [ ] **State handlers**: Provider implements all given() states
- [ ] **can-i-deploy**: Blocks deployment if contracts incompatible
- [ ] **Webhooks configured**: Consumer changes trigger provider verification
- [ ] **Retention policy**: Old pacts archived (keep 30 days, all production tags)
- [ ] **Resilience tested**: Timeouts, retries, error codes in contracts

## Integration Points

- Used in workflows: `*automate` (integration test generation), `*ci` (contract CI setup)
- Related fragments: `test-levels-framework.md`, `ci-burn-in.md`
- Tools: Pact.js, Pact Broker (Pactflow or self-hosted), Pact CLI

_Source: Pact consumer/provider sample repos, Murat contract testing blog, Pact official documentation_
