Testing Next Stack

Scaffold complete testing infrastructure for Next.js applications with modern testing tools.

Overview

To create a comprehensive testing setup for Next.js applications, use this skill to generate:

• Vitest configuration for fast unit tests
• React Testing Library setup for component testing
• Playwright configuration for E2E testing
• Accessibility testing with axe-core
• Test utilities and helpers
• Example test files demonstrating best practices

When to Use

Use this skill when:

• Starting a new Next.js project requiring test infrastructure
• Migrating from Jest to Vitest
• Adding E2E testing with Playwright
• Implementing accessibility testing requirements
• Creating test utilities for worldbuilding app features (entities, relationships, timelines)
• Standardizing testing patterns across projects

Setup Process

1. Analyze Project Structure

To understand the project layout, examine:

• Package.json for existing dependencies
• Next.js version and configuration
• TypeScript or JavaScript setup
• Existing testing infrastructure
• Component architecture

2. Install Dependencies

Generate package.json additions using scripts/generate_test_deps.py:

python scripts/generate_test_deps.py --nextjs-version <version> --typescript

Install required packages:

• vitest - Fast unit test runner
• @testing-library/react - Component testing utilities
• @testing-library/jest-dom - Custom matchers
• @testing-library/user-event - User interaction simulation
• @playwright/test - E2E testing framework
• @axe-core/playwright - Accessibility testing
• @vitejs/plugin-react - Vite React plugin
• jsdom - DOM implementation for Vitest

3. Generate Configuration Files

Create configuration files using templates from assets/:

Vitest Configuration (vitest.config.ts):

• Use template from assets/vitest.config.ts
• Configure path aliases matching Next.js
• Set up test environment (jsdom)
• Configure coverage reporting

Playwright Configuration (playwright.config.ts):

• Use template from assets/playwright.config.ts
• Configure browsers (chromium, firefox, webkit)
• Set baseURL for development server
• Configure screenshot and video capture
• Set up test artifacts directory

Test Setup (test/setup.ts):

• Use template from assets/test-setup.ts
• Import @testing-library/jest-dom
• Configure global test utilities
• Set up mock implementations

4. Create Test Utilities

Generate utility functions in test/utils/:

Render Utilities (test/utils/render.tsx):

• Custom render function wrapping providers
• Context providers (auth, theme, data)
• Router mocking for Next.js
• Query client setup for React Query

Mock Factories (test/utils/factories.ts):

• Entity mock data generators
• Relationship mock data
• User mock data
• API response mocks

Test Helpers (test/utils/helpers.ts):

• Async test utilities
• DOM query shortcuts
• Accessibility test helpers
• Custom matchers

5. Generate Example Tests

Create example test files demonstrating patterns:

Unit Test Example (test/unit/example.test.ts):

• Use template from assets/examples/unit-test.ts
• Demonstrate pure function testing
• Show async function testing
• Include edge case coverage

Component Test Example (test/component/example.test.tsx):

• Use template from assets/examples/component-test.tsx
• Demonstrate rendering and assertions
• Show user interaction testing
• Include accessibility checks with axe

E2E Test Example (test/e2e/example.spec.ts):

• Use template from assets/examples/e2e-test.ts
• Demonstrate user flow testing
• Show authentication flows
• Include accessibility scanning

6. Update Package Scripts

Add test scripts to package.json:

{
  "scripts": {
    "test": "vitest",
    "test:ui": "vitest --ui",
    "test:coverage": "vitest --coverage",
    "test:e2e": "playwright test",
    "test:e2e:ui": "playwright test --ui",
    "test:e2e:debug": "playwright test --debug"
  }
}

Test Patterns

Unit Testing with Vitest

To test utility functions and business logic:

import { describe, it, expect } from 'vitest'
import { validateEntityRelationship } from '@/lib/validation'

describe('validateEntityRelationship', () => {
  it('validates valid relationship', () => {
    const result = validateEntityRelationship({
      sourceId: '1',
      targetId: '2',
      type: 'BELONGS_TO'
    })
    expect(result.isValid).toBe(true)
  })

  it('rejects self-referential relationship', () => {
    const result = validateEntityRelationship({
      sourceId: '1',
      targetId: '1',
      type: 'BELONGS_TO'
    })
    expect(result.isValid).toBe(false)
  })
})

Component Testing with RTL

To test React components:

import { render, screen } from '@/test/utils/render'
import { userEvent } from '@testing-library/user-event'
import { axe } from '@axe-core/playwright'
import EntityCard from '@/components/EntityCard'

describe('EntityCard', () => {
  it('renders entity information', () => {
    render(<EntityCard entity={mockEntity} />)
    expect(screen.getByText(mockEntity.name)).toBeInTheDocument()
  })

  it('handles edit action', async () => {
    const onEdit = vi.fn()
    render(<EntityCard entity={mockEntity} onEdit={onEdit} />)

    await userEvent.click(screen.getByRole('button', { name: /edit/i }))
    expect(onEdit).toHaveBeenCalledWith(mockEntity.id)
  })

  it('has no accessibility violations', async () => {
    const { container } = render(<EntityCard entity={mockEntity} />)
    const results = await axe(container)
    expect(results.violations).toHaveLength(0)
  })
})

E2E Testing with Playwright

To test complete user flows:

import { test, expect } from '@playwright/test'
import { injectAxe, checkA11y } from '@axe-core/playwright'

test('user creates new entity', async ({ page }) => {
  await page.goto('/entities')

  // Inject axe for accessibility testing
  await injectAxe(page)

  // Navigate to create form
  await page.getByRole('button', { name: /create entity/i }).click()

  // Fill form
  await page.getByLabel(/name/i).fill('New Character')
  await page.getByLabel(/type/i).selectOption('character')
  await page.getByLabel(/description/i).fill('A mysterious traveler')

  // Submit
  await page.getByRole('button', { name: /save/i }).click()

  // Verify success
  await expect(page.getByText('New Character')).toBeVisible()

  // Check accessibility
  await checkA11y(page)
})

Accessibility Testing

Component-Level A11y

To add accessibility assertions in component tests:

import { render } from '@/test/utils/render'
import { axe, toHaveNoViolations } from 'jest-axe'

expect.extend(toHaveNoViolations)

it('meets accessibility standards', async () => {
  const { container } = render(<MyComponent />)
  const results = await axe(container)
  expect(results).toHaveNoViolations()
})

E2E A11y Scanning

To scan entire pages for accessibility issues:

import { test } from '@playwright/test'
import { injectAxe, checkA11y, getViolations } from '@axe-core/playwright'

test('homepage accessibility', async ({ page }) => {
  await page.goto('/')
  await injectAxe(page)

  // Check entire page
  await checkA11y(page)

  // Or check specific element
  await checkA11y(page, '#main-content')

  // Or get violations for custom reporting
  const violations = await getViolations(page)
  expect(violations).toHaveLength(0)
})

Coverage Configuration

To generate code coverage reports, configure Vitest coverage in vitest.config.ts:

export default defineConfig({
  test: {
    coverage: {
      provider: 'v8',
      reporter: ['text', 'json', 'html'],
      exclude: [
        'node_modules/',
        'test/',
        '**/*.config.{ts,js}',
        '**/*.d.ts'
      ],
      thresholds: {
        lines: 80,
        functions: 80,
        branches: 80,
        statements: 80
      }
    }
  }
})

Resources

Consult the following resources for detailed information:

• references/vitest-setup.md - Vitest configuration details
• references/rtl-patterns.md - React Testing Library best practices
• references/playwright-setup.md - Playwright configuration guide
• references/a11y-testing.md - Accessibility testing guidelines
• assets/vitest.config.ts - Vitest configuration template
• assets/playwright.config.ts - Playwright configuration template
• assets/test-setup.ts - Test setup template
• assets/examples/ - Example test files

Next Steps

After scaffolding the testing infrastructure:

1. Run npm install to install dependencies
2. Execute npm test to verify Vitest setup
3. Execute npm run test:e2e to verify Playwright setup
4. Review and customize configuration files
5. Add tests for existing components and features
6. Configure CI/CD pipeline with test execution
7. Set up coverage reporting in CI
8. Document testing guidelines for team