08. Testing & quality
How you make sure code actually works — and keeps working as it changes. Covers the testing pyramid (unit, integration, end-to-end), plus the surrounding quality tools (linting, type checking, formatting).
Entries
| # | Entry | Status | One-line description |
|---|---|---|---|
| 1 | Why test? | 🟩 COMPLETE | The real costs of not testing — and the trap of testing too much |
| 2 | Unit tests | 🟩 COMPLETE | Small, fast tests of individual functions |
| 3 | Integration tests | 🟩 COMPLETE | Tests that exercise multiple parts together |
| 4 | End-to-end (E2E) tests | 🟩 COMPLETE | Tests that drive the real browser like a user — Playwright, Cypress |
| 5 | Linting | 🟩 COMPLETE | Automated rule-checks for code style and common mistakes |
| 6 | Type checking | 🟩 COMPLETE | TypeScript’s tsc — catching whole classes of bugs before runtime |
| 7 | Code review | 🟩 COMPLETE 🟦 LIVING | Why a second pair of eyes (or an AI) on a PR matters |
Suggested reading order
1 → 5 → 6 → 2 → 3 → 4 → 7. Linting and type checking are the cheapest wins; tests are higher-investment.
See also
- 02. Frontend — TypeScript
- 11. AI-assisted development — Claude as a code reviewer