Frontend Testing

Desktop Ethereal Frontend Testing Skill

This skill enables Claude to generate high-quality, comprehensive frontend tests for the Desktop Ethereal project following established conventions and best practices.

⚠️ Authoritative Source: This skill is derived from general testing best practices with adaptations for Tauri/React desktop applications. Use Vitest mock/timer APIs (vi.*).

When to Apply This Skill

Apply this skill when the user:

• Asks to write tests for a component, hook, or utility
• Asks to review existing tests for completeness
• Mentions Vitest, React Testing Library, RTL, or spec files
• Requests test coverage improvement
• Mentions testing, unit tests, or integration tests for frontend code

Do NOT apply when:

• User is asking about backend/Rust tests
• User is asking about E2E tests (Playwright/Cypress)
• User is only asking conceptual questions without code context

Quick Reference

Tech Stack

Key Commands

# Run all tests
pnpm test

# Watch mode
pnpm test:watch

# Run specific file
pnpm test path/to/file.spec.tsx

# Generate coverage report
pnpm test:coverage

File Naming

• Test files: ComponentName.test.tsx (same directory as component)
• Integration tests: src/test/integration/ directory

Test Structure Template

import { render, screen, fireEvent, waitFor } from '@testing-library/react'
import Component from './index'

// ✅ Import real project components (DO NOT mock these)
// import Sprite from '@/components/Sprite'
// import { useEtherealState } from '@/hooks/useEtherealState'

// ✅ Mock external dependencies and Tauri APIs only
vi.mock('@tauri-apps/api/event', () => ({
  listen: vi.fn().mockResolvedValue({ unlisten: vi.fn() }),
}))

vi.mock('@tauri-apps/api/core', () => ({
  invoke: vi.fn(),
}))

// Shared state for mocks (if needed)
let mockSharedState = false

describe('ComponentName', () => {
  beforeEach(() => {
    vi.clearAllMocks()  // ✅ Reset mocks BEFORE each test
    mockSharedState = false  // ✅ Reset shared state
  })

  // Rendering tests (REQUIRED)
  describe('Rendering', () => {
    it('should render without crashing', () => {
      // Arrange
      const props = { title: 'Test' }

      // Act
      render(<Component {...props} />)

      // Assert
      expect(screen.getByText('Test')).toBeInTheDocument()
    })
  })

  // Props tests (REQUIRED)
  describe('Props', () => {
    it('should apply custom className', () => {
      render(<Component className="custom" />)
      expect(screen.getByRole('button')).toHaveClass('custom')
    })
  })

  // User Interactions
  describe('User Interactions', () => {
    it('should handle click events', () => {
      const handleClick = vi.fn()
      render(<Component />)

      fireEvent.click(screen.getByRole('button'))

      expect(handleClick).toHaveBeenCalledTimes(1)
    })
  })

  // Edge Cases (REQUIRED)
  describe('Edge Cases', () => {
    it('should handle null data', () => {
      render(<Component data={null} />)
      expect(screen.getByText(/no data/i)).toBeInTheDocument()
    })

    it('should handle empty array', () => {
      render(<Component items={[]} />)
      expect(screen.getByText(/empty/i)).toBeInTheDocument()
    })
  })
})

Testing Workflow (CRITICAL)

⚠️ Incremental Approach Required

NEVER generate all test files at once. For complex components or multi-file directories:

1. Analyze & Plan: List all files, order by complexity (simple → complex)
2. Process ONE at a time: Write test → Run test → Fix if needed → Next
3. Verify before proceeding: Do NOT continue to next file until current passes

For each file:
  ┌────────────────────────────────────────┐
  │ 1. Write test                          │
  │ 2. Run: pnpm test <file>.test.tsx      │
  │ 3. PASS? → Mark complete, next file    │
  │    FAIL? → Fix first, then continue    │
  │ 4. Check coverage                      │
  └────────────────────────────────────────┘

Complexity-Based Order

Process in this order for multi-file testing:

1. 🟢 Utility functions (simplest)
2. 🟢 Custom hooks
3. 🟡 Simple components (presentational)
4. 🟡 Medium components (state, effects)
5. 🔴 Complex components (API, routing)
6. 🔴 Integration tests (App component - last)

When to Refactor First

• Complexity > 50: Break into smaller pieces before testing
• 500+ lines: Consider splitting before testing
• Many dependencies: Extract logic into hooks first

📖 See references/workflow.md for complete workflow details and todo list format.

Testing Strategy

Path-Level Testing (Directory Testing)

When assigned to test a directory/path, test ALL content within that path:

• Test all components, hooks, utilities in the directory (not just index file)
• Use incremental approach: one file at a time, verify each before proceeding
• Goal: 100% coverage of ALL files in the directory

Integration Testing First

Prefer integration testing when writing tests for a directory:

• ✅ Import real project components directly (including base components and siblings)
• ✅ Only mock: Tauri APIs (@/tauri-apps/api/*), external services
• ❌ DO NOT mock project components unless absolutely necessary
• ❌ DO NOT mock sibling/child components in the same directory

See Test Structure Template for correct import/mock patterns.

Core Principles

1. AAA Pattern (Arrange-Act-Assert)

Every test should clearly separate:

• Arrange: Setup test data and render component
• Act: Perform user actions
• Assert: Verify expected outcomes

2. Black-Box Testing

• Test observable behavior, not implementation details
• Use semantic queries (getByRole, getByLabelText)
• Avoid testing internal state directly
• Prefer pattern matching over hardcoded strings in assertions:

// ❌ Avoid: hardcoded text assertions
expect(screen.getByText('Loading...')).toBeInTheDocument()

// ✅ Better: role-based queries
expect(screen.getByRole('status')).toBeInTheDocument()

// ✅ Better: pattern matching
expect(screen.getByText(/loading/i)).toBeInTheDocument()

3. Single Behavior Per Test

Each test verifies ONE user-observable behavior:

// ✅ Good: One behavior
it('should disable button when loading', () => {
  render(<Button loading />)
  expect(screen.getByRole('button')).toBeDisabled()
})

// ❌ Bad: Multiple behaviors
it('should handle loading state', () => {
  render(<Button loading />)
  expect(screen.getByRole('button')).toBeDisabled()
  expect(screen.getByText('Loading...')).toBeInTheDocument()
  expect(screen.getByRole('button')).toHaveClass('loading')
})

4. Semantic Naming

Use should <behavior> when <condition>:

it('should show error message when validation fails')
it('should call onSubmit when form is valid')
it('should disable input when isReadOnly is true')

Required Test Scenarios

Always Required (All Components)

1. Rendering: Component renders without crashing
2. Props: Required props, optional props, default values
3. Edge Cases: null, undefined, empty values, boundary conditions

Conditional (When Present)

Coverage Goals (Per File)

For each test file generated, aim for:

• ✅ 100% function coverage
• ✅ 100% statement coverage
• ✅ >95% branch coverage
• ✅ >95% line coverage

Note: For multi-file directories, process one file at a time with full coverage each. See references/workflow.md.

Tauri-Specific Considerations

Mocking Tauri APIs

Always mock Tauri APIs in tests:

// Mock Tauri event system
vi.mock('@tauri-apps/api/event', () => ({
  listen: vi.fn().mockImplementation((event, callback) => {
    // Simulate event emission for testing
    return Promise.resolve({ unlisten: vi.fn() })
  }),
}))

// Mock Tauri command invocations
vi.mock('@tauri-apps/api/core', () => ({
  invoke: vi.fn().mockResolvedValue('mock result'),
}))

Testing Event-Driven Components

For components that respond to Tauri events:

it('should update state when gpu-update event is received', async () => {
  // Mock the listen function to immediately call the callback
  const mockListen = vi.mocked(listen)
  mockListen.mockImplementation((event, callback) => {
    if (event === 'gpu-update') {
      callback({ payload: { temperature: 85 } })
    }
    return Promise.resolve({ unlisten: vi.fn() })
  })

  render(<EtherealStatusBar />)

  // Wait for state update
  await waitFor(() => {
    expect(screen.getByText('OVERHEATING')).toBeInTheDocument()
  })
})

Detailed Guides

For more detailed information, refer to:

• references/workflow.md - Incremental testing workflow (MUST READ for multi-file testing)
• references/mocking.md - Mock patterns and best practices
• references/async-testing.md - Async operations and API calls
• references/common-patterns.md - Frequently used testing patterns
• references/checklist.md - Test generation checklist and validation steps

Authoritative References

Primary Specification (MUST follow)

• docs/testing.md - The canonical testing specification for Desktop Ethereal.

Reference Examples in Codebase

• src/hooks/useEtherealState.test.ts - Custom hook tests
• src/components/Sprite.test.tsx - Component tests (to be created)
• src/test/setup.ts - Global test setup

Project Configuration

• vitest.config.ts - Vitest configuration
• src/test/setup.ts - Test environment setup