testing

Testing Specialist

You are an expert at testing TypeScript/React applications using Playwright, Vitest, and Storybook.

When To Use

Claude should automatically use this skill when:

• User asks to write tests or improve coverage
• User mentions Playwright, Vitest, E2E, unit tests
• Debugging test failures
• Setting up test infrastructure

Testing Stack

CRITICAL: Read Before Write (Reconnaissance-Then-Action)

Before writing ANY E2E test, you MUST:

1. Read the component source file (e.g., Toolbar.tsx, Editor.tsx)
2. Identify stable selectors in this priority order:
   • data-testid attributes (explicit testing contract)
   • title attributes (accessibility, stable)
   • aria-label attributes (accessibility)
   • Text content (fragile, last resort)
3. Extract exact values from the source - never guess or assume

Selector Priority (Playwright Official)

NEVER use: CSS classes, XPath, or auto-generated IDs

Anti-Pattern: Speculative Selectors

// ❌ WRONG - Guessing without reading source
await editor.clickToolbarButton('B');  // Assumes button text is "B"

// ✅ CORRECT - After reading Toolbar.tsx:54 shows title="Bold (Cmd+B)"
await editor.clickToolbarButton('Bold (Cmd+B)');

data-testid Convention

When adding test IDs to components, use format: {scope}-{element}-{type}

data-testid="toolbar-bold-button"
data-testid="editor-content-area"
data-testid="sidebar-note-list"

Playwright E2E Tests

File Structure

e2e/
├── fixtures/
│   └── editor-helpers.ts   # Shared test utilities
├── editor.spec.ts          # Editor functionality
├── formatting.spec.ts      # Text formatting
├── headings.spec.ts        # Heading toggles
├── lists.spec.ts           # List operations
├── blocks.spec.ts          # Block elements
├── keyboard-shortcuts.spec.ts
├── toolbar.spec.ts
└── history.spec.ts

Test Pattern

import { test, expect } from '@playwright/test';
import { EditorHelper } from './fixtures/editor-helpers';

test.describe('Feature Name', () => {
  let editor: EditorHelper;

  test.beforeEach(async ({ page }) => {
    editor = new EditorHelper(page);
    await editor.goto();
  });

  test('descriptive test name', async () => {
    await editor.type('test content');
    await editor.selectAll();
    // Use title from Toolbar.tsx - NOT guessed text
    await editor.clickToolbarButton('Bold (Cmd+B)');
    await editor.expectElement('strong');
  });
});

EditorHelper Methods

editor.goto()                      // Navigate to app
editor.clear()                     // Clear editor content
editor.type(text)                  // Type text
editor.selectAll()                 // Select all (Cmd+A)
editor.clickToolbarButton(title)   // Click toolbar button by title attribute
editor.isToolbarButtonActive(title) // Check button state by title
editor.expectText(text)            // Assert text exists
editor.expectElement(selector)     // Assert element exists
editor.pressShortcut(key)          // Press keyboard shortcut

Toolbar Button Titles (from Toolbar.tsx)

Commands

pnpm test:e2e           # Run all E2E tests
pnpm test:e2e:ui        # Open Playwright UI
pnpm test:e2e:headed    # Run with browser visible
pnpm test:e2e:chromium  # Chrome only
pnpm test:e2e:webkit    # Safari only

Vitest Unit Tests

File Naming

• Component: ComponentName.test.tsx
• Hook: useHookName.test.ts
• Utility: utilName.test.ts

Test Pattern

import { describe, it, expect, vi } from 'vitest';
import { functionName } from './module';

describe('functionName', () => {
  it('should do something', () => {
    const result = functionName(input);
    expect(result).toBe(expected);
  });

  it('should handle edge case', () => {
    expect(() => functionName(null)).toThrow();
  });
});

Hook Testing

import { renderHook, act } from '@testing-library/react';
import { useHookName } from './useHookName';

describe('useHookName', () => {
  it('should return initial state', () => {
    const { result } = renderHook(() => useHookName());
    expect(result.current.value).toBe(initial);
  });

  it('should update on action', async () => {
    const { result } = renderHook(() => useHookName());
    await act(async () => {
      await result.current.doAction();
    });
    expect(result.current.value).toBe(updated);
  });
});

Storybook Interaction Tests

import { within, userEvent, expect } from '@storybook/test';

export const WithInteraction: Story = {
  play: async ({ canvasElement }) => {
    const canvas = within(canvasElement);

    // Find and interact with elements
    const button = canvas.getByRole('button', { name: 'Submit' });
    await userEvent.click(button);

    // Assert results
    await expect(canvas.getByText('Success')).toBeInTheDocument();
  },
};

Test Checklist

When writing tests:

• Test happy path (expected behavior)
• Test edge cases (empty, null, boundary values)
• Test error handling
• Test loading/async states
• Use descriptive test names
• Keep tests focused and isolated
• Mock external dependencies
• Avoid testing implementation details

Coverage Goals