Agent-Skills.md

Agent Skills: Next.js Testing

Write Vitest unit tests with React Testing Library and Playwright E2E tests for Next.js App Router projects. Use when testing components with RTL, mocking APIs with MSW, or creating Playwright user flow tests. (triggers: **/*.test.{ts,tsx}, cypress/**, tests/**, vitest, playwright, msw, testing-library)

UncategorizedID: hoangnguyen0403/agent-skills-standard/nextjs-testing

Repository

hoangnguyen0403/agent-skills-standard
HoangNguyen0403License: Apache-2.0
362103

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pnpm dlx add-skill https://github.com/HoangNguyen0403/agent-skills-standard/tree/HEAD/skills/nextjs/nextjs-testing

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skills/nextjs/nextjs-testing/SKILL.md

Skill Metadata

Name
nextjs-testing
Description
"Write Vitest unit tests with React Testing Library and Playwright E2E tests for Next.js App Router projects. Use when testing components with RTL, mocking APIs with MSW, or creating Playwright user flow tests. (triggers: **/*.test.{ts,tsx}, cypress/**, tests/**, vitest, playwright, msw, testing-library)"

Next.js Testing

Priority: P1 (HIGH)

Workflow: Test a New Feature

  1. Write unit tests — Use Vitest + RTL with Arrange-Act-Assert pattern.
  2. Mock APIs — Set up MSW handlers for all fetch boundaries.
  3. Test interactions — Use userEvent (async) for clicks, typing, form submissions.
  4. Add E2E tests — Use Playwright for critical user flows (login, checkout).
  5. Verify coverage — Aim for 80%+ on core libraries via JSON coverage reports.

Component Test Example

See implementation examples

Structure

See implementation examples

Implementation Guidelines

  • Unit Testing: Use Vitest for speed and React Testing Library (RTL) for component behavior. Follow Arrange-Act-Assert (AAA) patterns.
  • E2E Testing: Use Playwright for full-stack App Router validation. Focus on User Flows (e.g., Login, Checkout).
  • Networking: Mock all internal/external API boundaries using Mock Service Worker (MSW). Ensure server and browser handlers are correctly configured.
  • RSC Testing: Test React Server Components (RSC) using the same patterns as libraries (SSR-compatible tests). Prefer E2E tests for complex async data-fetching logic.
  • Interactions: Use userEvent (async) to simulate user actions: await user.click(button).
  • Selectors: Favor getByRole / findByRole to test accessibility. Use data-testid only as a fallback.
  • Environment: Configure vitest.config.ts with jsdom or happy-dom for component tests.
  • Reporting: Ensure tests generate JSON coverage reports for CI gates. Aim for 80%+ coverage on core libraries.

Anti-Patterns

  • No real network usage in tests: Always use MSW handlers or mocks.
  • No implementation testing: Test user behavior, not internal methods.
  • No heavy E2E for unit logic: Use Vitest for isolated logic tests.
  • No global state leakage: Reset MSW handlers and mocks after each test.

References