Advanced GitHub Actions

Course 2, Chapter 8 covered a single straightforward test workflow. Real projects usually need more: testing across multiple versions at once, using credentials safely, avoiding redundant work on every run, and — the natural endpoint — automatically deploying when everything passes.

Matrix Builds — Testing Multiple Configurations at Once

A matrix runs the same job multiple times with different variable combinations — typically used to test against several language versions or operating systems simultaneously, in parallel, rather than one at a time.

This single definition produces three separate, parallel job runs:

Secrets — Using Credentials Safely in CI

Course 1, Chapter 6 established that secrets never belong in committed code. Actions workflows often genuinely need credentials (a deploy token, an API key for a test run) — GitHub Secrets is the answer: encrypted values stored at the repo or organisation level, injected into workflows at runtime without ever appearing in logs or the YAML file itself.

Set up under Settings → Secrets and variables → Actions → New repository secret. The actual value is never visible again after saving, even to repo admins — only usable inside workflow runs.

Caching — Avoiding Redundant Work

Every job starts on a completely fresh virtual machine (Course 2, Chapter 8) — meaning npm install re-downloads every dependency, every single run, unless you cache them.

The cache: 'npm' option (built directly into setup-node) keys the cache to your lockfile's hash — if package-lock.json hasn't changed since the last run, dependencies restore from cache almost instantly instead of re-downloading.

A Complete Deployment Pipeline

Bringing it together — test, then deploy only if tests pass, only on the main branch:

Reusable Workflows — Avoiding Duplication Across Repos

For teams running near-identical CI across several repositories, a workflow can call another workflow as a reusable building block, rather than copy-pasting the same YAML everywhere.