CI/CD ›

Choosing a CI/CD platform, structuring pipelines, and testing strategies that keep feedback fast.

GitHub Actions

Best for: GitHub-hosted projects, easy integration

# Example: Python app with GitHub Actions
name: Python CI
on: [push]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v4
    - uses: actions/setup-python@v5
      with:
        python-version: '3.12'
    - run: |
        pip install -r requirements.txt
        pytest

Recent GitHub Actions Features:

  • Larger runners: Up to 64 vCPUs and 256 GB RAM
  • GPU runners: NVIDIA GPU support for ML workloads
  • Arm64 runners: Native ARM architecture support
  • Deployment protection rules: Environment-specific approvals

GitLab CI/CD

Best for: GitLab users, built-in DevOps features

# .gitlab-ci.yml
stages:
  - test
  - build
  - deploy

test:
  stage: test
  script:
    - npm install
    - npm test

deploy:
  stage: deploy
  script:
    - npm run build
    - npm run deploy
  only:
    - main

Jenkins

Best for: Complex workflows, self-hosted, plugins

// Jenkinsfile
pipeline {
    agent any

    stages {
        stage('Build') {
            steps {
                sh 'mvn clean package'
            }
        }
        stage('Test') {
            steps {
                sh 'mvn test'
            }
        }
        stage('Deploy') {
            steps {
                sh './deploy.sh'
            }
        }
    }
}

CircleCI

Best for: Fast builds, Docker support

# .circleci/config.yml
version: 2.1
jobs:
  build-and-test:
    docker:
      - image: cimg/node:18.0
    steps:
      - checkout
      - run: npm install
      - run: npm test
      - run: npm run build

workflows:
  main:
    jobs:
      - build-and-test

Platform Comparison

Platform Pros Cons Best Use Case
GitHub Actions Free for public repos, great integration Limited free minutes for private GitHub projects
GitLab CI Complete DevOps platform Can be complex Full DevOps lifecycle
Jenkins Highly customizable, mature Requires maintenance Enterprise, complex needs
CircleCI Fast, good caching Can get expensive Speed-critical projects
Travis CI Simple setup Less popular now Legacy projects
Azure DevOps Great for .NET Microsoft-centric Windows/Azure shops
Buildkite Hybrid model, scalable Requires own runners High-security needs
Drone Container-native, simple Smaller community Kubernetes environments

Pipeline Design Patterns

1. Simple Linear Pipeline

stages:
  - build
  - test
  - deploy

Use when: Starting out, simple projects

2. Parallel Execution

test:
  parallel:
    - unit-tests:
        script: npm run test:unit
    - integration-tests:
        script: npm run test:integration
    - lint:
        script: npm run lint

Use when: Tests are independent, need speed

3. Matrix Builds

strategy:
  matrix:
    node-version: [14, 16, 18]
    os: [ubuntu-latest, windows-latest]

Use when: Testing across multiple environments

4. Fan-out/Fan-in

stages:
  - build
  - parallel-tests  # Fan-out: multiple parallel jobs
  - aggregate       # Fan-in: collect results
  - deploy

Use when: Complex test suites, need aggregated results

5. Blue-Green Pipeline

deploy-blue:
  script: deploy_to_blue_environment()

smoke-test:
  script: test_blue_environment()

switch-traffic:
  script: route_traffic_to_blue()

cleanup-green:
  script: teardown_green_environment()

Use when: Zero-downtime deployments critical (see Deployment Strategies for the full pattern)

Testing Strategies in CI/CD

The Testing Pyramid

        /\
       /  \  E2E Tests (Slow, Few)
      /    \
     /------\ Integration Tests (Medium)
    /        \
   /----------\ Unit Tests (Fast, Many)

Unit Tests in CI

// Fast, isolated tests
describe('Calculator', () => {
  it('adds two numbers', () => {
    expect(add(2, 3)).toBe(5);
  });
});

Run on: Every commit Duration: < 5 minutes

Integration Tests

// Test component interactions
describe('API Integration', () => {
  it('creates user and sends email', async () => {
    const user = await createUser(data);
    expect(emailService.sent).toBe(true);
  });
});

Run on: Pull requests Duration: 5-15 minutes

End-to-End Tests

// Test complete user flows
describe('Checkout Flow', () => {
  it('completes purchase', async () => {
    await login();
    await addToCart();
    await checkout();
    expect(orderConfirmation).toBeVisible();
  });
});

Run on: Pre-deployment Duration: 15-60 minutes

Performance Tests

performance-test:
  script:
    - k6 run load-test.js
  rules:
    - if: $CI_COMMIT_BRANCH == "main"

See Also