GitHub Actions: Jobs, Steps, Matrix, and Reusable Building Blocks

- uses: actions/checkout@v4

# Fetch the repo in a workflow job.

- uses: actions/setup-node@v4
  with:
    node-version: 20

# Install a specific Node.js version for the job.

- name: Publish
  if: github.ref == 'refs/heads/main'
  run: npm run publish

# Use expressions with `if` to gate steps.

jobs:
  release:
    if: startsWith(github.ref, 'refs/tags/')
    runs-on: ubuntu-latest

# Gate a full job on a tag-based release.

- name: Optional audit
  continue-on-error: true
  run: npm audit

# Continue the job even if a step fails.

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

# Use a strategy matrix for version coverage.

strategy:
  matrix:
    os: [ubuntu-latest, macos-latest, windows-latest]

runs-on: ${{ matrix.os }}

# Validate portability across Linux, macOS, and Windows.

services:
  postgres:
    image: postgres:16
    env:
      POSTGRES_PASSWORD: postgres
    ports:
      - 5432:5432
    options: >-
      --health-cmd "pg_isready -U postgres"
      --health-interval 10s
      --health-timeout 5s
      --health-retries 5

# Run integration tests against a database service.

jobs:
  ci:
    uses: my-org/my-repo/.github/workflows/reusable-ci.yml@main
    with:
      node-version: 20
    secrets: inherit

# Centralize shared CI logic in one workflow file.

name: setup-project
runs:
  using: "composite"
  steps:
    - run: npm ci
      shell: bash
    - run: npm run build
      shell: bash

# Bundle repeated shell steps into a reusable local action.