Consumer Driven Contracts (CDC)

CDC provides a way to define mock provider for consumer and verify contracts against provider. It is written in JavaScript, however can be run in any setup using docker.

Getting started

Using docker-compose

version: '2'
services:
  api:
    build:
      context: .
    depends_on:
      - dependency
    command: npm start
  dependency:
    image: uldissturms/cdc
    volumes:
      - ./contracts/dependency:/usr/app/src/contracts
    command: mock
    ports:
      - "3000:3000"

Where ./contracts/dependency contains index.js that describes contract.

./contracts
└── dependency
    └── index.js

Using docker

docker run -p 3000:3000 -v ${PWD}/contracts:/usr/app/src/contracts uldissturms/cdc mock ./contracts/simple

Using npm

npm i cdc
./node_modules/.bin/cdc mock ./contracts/simple
./node_modules/.bin/cdc verify ./contracts/simple --baseUrl http://localhost:3000

Contracts

Simple contract with schema validation

const joi = require('joi')

module.exports = {
  name: 'simple request/response schema',
  request: {
    path: '/api/simple-schema',
    method: 'POST',
    headers: {
      'content-type': 'application/json'
    },
    body: {
      hello: 'world'
    },
    bodySchema: joi.object().keys({
      hello: joi.string()
    })
  },
  response: {
    body: {
      id: 12345
    },
    bodySchema: joi.object().keys({
      id: joi.number().integer()
    })
  }
}

Response

curl localhost:3000/api/simple-schema -H 'content-type: application/json' -d '{"hello": "world"}'

{"id": 12345}

Usage

Why I wrote my own

• mock - mocks responses for consumer
• verify - verifies contracts agains provider

Options

• mock
  • --port, -p - port for running mock server, defaults to 3000 (optional)
  • --no-cors, -C - disable CORS support (optional)
  • --watch, -w - to watch current directory for contract changes (optional)
  • --tls, -t - enable TLS with a self signed certificate ( setting NODE_TLS_REJECT_UNAUTHORIZED=0 when consuming from node might be required )
• verify
  • --baseUrl, -b - base url to run verifications against (required)

Examples

For more examples take a look at contracts in ./contracts used for tests.

Libraries used

• Joi (schema valiations)
• Hapi (mock provider server)
• Tape (verify consumer contracts against a provider)

Influences

• consumer-contracts
• mockingjay-server
• pact
• pacto

Further reading

• Consumer-Driven Contracts: A Service Evolution Pattern
• Integration Contract Test
• Why I wrote my own

Licence

MIT