Intro to GitHub Actions

GitHub Actions is a built-in CI/CD platform on GitHub. Define automation workflows that trigger on events like code pushes, pull requests, or schedules. Run tests, build apps, and deploy code — all from YAML files in your repository.

01.Core Concepts

Workflow: a YAML file in .github/workflows/ that defines the entire automation pipeline. Event: what triggers it (push, pull_request, schedule, workflow_dispatch). Job: a group of steps running on one virtual machine. Step: a single unit — run a shell command or use a pre-built Action from the marketplace. Runner: the VM environment (ubuntu-latest, windows-latest, macos-latest).

Commit Timeline

a1b2c3d

init

b2c3d4e

feat

c3d4e5f

fix

d4e5f6a

HEAD

02.A Real CI Workflow

On every push and pull request to main: check out the code, set up Node.js, install dependencies (npm ci — faster than npm install), run linting, run unit tests. If any step exits with a non-zero code, the job fails, you get an email notification, and GitHub shows a red ✗ on the commit. PRs cannot be merged until the checks pass.

Distributed Architecture

💻

Your Local

push / pull

☁️

GitHub (Remote)

push / pull

💻

Teammate's Local

Commands

commands — click to reveal output

mkdir -p .github/workflows

Create the workflows directory

# .github/workflows/ci.yml

Create your workflow file here

# Workflow structure:
# name: CI
# on: [push, pull_request]
# jobs:
#   test:
#     runs-on: ubuntu-latest
#     steps:
#       - uses: actions/checkout@v4
#       - uses: actions/setup-node@v4
#         with: { node-version: 20 }
#       - run: npm ci
#       - run: npm test

Basic CI workflow YAML

git add .github/ && git commit -m "Add CI workflow"

Commit and push to activate the workflow

gh run list

View recent workflow run results

▼ show output

gh run watch

Watch a live workflow run in real time

KNOWLEDGE CHECK

What format are GitHub Actions workflow files written in?

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