GitHub Actions

Here's a common scenario: you push code to GitHub, then manually run tests on your local machine, then manually deploy to your server. That's tedious. What if all that happened automatically?

That's exactly what GitHub Actions does.

What's CI/CD?

Before we dive in, let's get the jargon straight:

• CI (Continuous Integration) - automatically run tests every time you push code
• CD (Continuous Deployment) - automatically deploy when tests pass

Together, they mean: push code → tests run → if it passes, it deploys. No human involvement required.

Your First Workflow

GitHub Actions lives in your repo. You create a workflow file and GitHub runs it when triggered.

Create a file at .github/workflows/test.yml in your repo:

name: Run Tests

on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    
    steps:
      - uses: actions/checkout@v4
      
      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '20'
      
      - name: Install dependencies
        run: npm ci
      
      - name: Run tests
        run: npm test

Let's break this down:

• on - when to run this (push or pull request)
• jobs - what to run (we call it "test")
• runs-on - what machine (ubuntu-latest)
• steps - individual actions to take

Now whenever you push, GitHub spins up a fresh Ubuntu machine, checks out your code, installs Node, and runs your tests. For free. (Up to a certain limit.)

Deploying When Tests Pass

Okay, tests pass. Now let's deploy—but only if everything worked:

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      # ... run tests ...
      
  deploy:
    needs: test
    if: github.ref == 'refs/heads/main'
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Deploy to server
        run: |
          echo "Deploying to production..."
          # Add your actual deploy commands here

The magic is needs: test. This tells GitHub: "don't run the deploy job until the test job completes successfully."

Also useful: if: github.ref == 'refs/heads/main' means "only deploy when pushing to main branch."

Common Things People Do

• Run test suites automatically
• Lint code (check for style errors)
• Build Docker images
• Deploy to cloud providers (AWS, Heroku, etc.)
• Send Slack notifications when deployments happen
• Run scheduled jobs (nightly builds, weekly reports)

Testing Multiple Versions

Want to make sure your code works on Node 16, 18, and 20? Matrix testing runs your tests on all versions at once:

jobs:
  test:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        node: [16, 18, 20, 22]
    steps:
      - uses: actions/setup-node@v4
        with:
          node-version: ${{ matrix.node }}
      - run: npm test

This spawns four parallel test jobs—one for each Node version. If any fail, you know immediately.

Is It Worth It?

Short answer: yes. Even for small projects.

Once set up, you never forget to run tests before deploying. You catch bugs before they reach production. And it's free for public repos (and has a generous free tier for private).

Start simple. Just run your tests on every push. Then add deployment later.