Testing Suite Skill

Overview

Set up and configure comprehensive testing for Storybook 9 components, including interaction tests with play functions, accessibility testing with axe-core, and visual regression testing with Playwright.

This skill provides guidance on implementing modern component testing patterns using Storybook 9's integrated testing capabilities.

What This Skill Provides

Testing Strategy Guidance

Configure the right testing setup based on:

• Project requirements: Unit, integration, or end-to-end testing
• Framework choice: React Testing Library, Vue Testing Library, Svelte Testing Library
• Testing scope: Interaction tests, accessibility, visual regression
• CI/CD integration: GitHub Actions, GitLab CI, CircleCI

Interaction Testing

Set up and write interaction tests using:

• Play functions: Simulate user interactions in stories
• Testing Library: Query elements by role, text, label
• User events: Click, type, keyboard, hover, focus
• Assertions: Verify component behavior and state

Accessibility Testing

Configure accessibility validation with:

• axe-core integration: WCAG 2.1 compliance checking
• ARIA validation: Roles, labels, descriptions
• Keyboard navigation: Tab order, focus management
• Screen reader support: Semantic HTML, announcements
• Color contrast: WCAG AA/AAA compliance

Visual Regression Testing

Set up visual regression tests with:

• Playwright integration: Real browser screenshots
• Snapshot comparisons: Detect unintended visual changes
• Cross-browser testing: Chromium, Firefox, WebKit
• Responsive testing: Multiple viewport sizes

Testing Levels

Level 1: Basic Stories

Stories with args and controls only (no automated tests).

Best for:

• Component showcases
• Design system documentation
• Quick prototyping

Setup:

export const Primary: Story = {
  args: {
    variant: 'primary',
    children: 'Button',
  },
};

Level 2: Interaction Tests

Stories with play functions that test user interactions.

Best for:

• Form components
• Interactive widgets
• State management verification

Setup:

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

export const WithInteraction: Story = {
  args: { children: 'Click me' },
  play: async ({ canvasElement }) => {
    const canvas = within(canvasElement);
    const button = canvas.getByRole('button');

    await expect(button).toBeInTheDocument();
    await userEvent.click(button);
    await expect(button).toHaveFocus();
  },
};

Level 3: Accessibility Tests

Stories with axe-core validation rules.

Best for:

• Public-facing applications
• Compliance requirements (WCAG 2.1)
• Accessible component libraries

Setup:

export const AccessibilityValidation: Story = {
  args: { children: 'Button' },
  parameters: {
    a11y: {
      config: {
        rules: [
          { id: 'button-name', enabled: true },
          { id: 'color-contrast', enabled: true },
          { id: 'focus-visible', enabled: true },
        ],
      },
    },
  },
};

Level 4: Full Testing Suite

Combination of interaction tests, accessibility tests, and visual regression.

Best for:

• Production applications
• Component libraries
• Critical user flows

Storybook 9 Testing Features

Vitest Integration

Storybook 9 uses Vitest as the default test runner:

Benefits:

• ⚡ Fast: Runs in real browsers (not JSDOM)
• 📦 Zero config: Works out of the box
• 🎯 Isolated: Each story runs in isolation
• 🔄 Watch mode: Instant feedback on changes

Setup: Add to package.json:

{
  "scripts": {
    "test-storybook": "test-storybook"
  }
}

Playwright Integration

Real browser testing with Playwright:

Benefits:

• 🌐 Real browsers: Chromium, Firefox, WebKit
• 📸 Screenshots: Visual regression testing
• 🎬 Video recording: Debug test failures
• 🔍 Tracing: Step-by-step execution

Setup: Storybook 9 includes Playwright by default. Configure in .storybook/test-runner-jest.config.js:

export default {
  browsers: ['chromium', 'firefox', 'webkit'],
  screenshot: 'only-on-failure',
  video: 'retain-on-failure',
};

Testing Library Integration

Query components using accessible selectors:

Recommended queries (in order of preference):

1. getByRole() - Semantic HTML roles
2. getByLabelText() - Form labels
3. getByPlaceholderText() - Input placeholders
4. getByText() - Visible text content
5. getByTestId() - Last resort only

Example:

const button = canvas.getByRole('button', { name: /submit/i });
const input = canvas.getByLabelText('Email address');
const heading = canvas.getByRole('heading', { level: 1 });

Common Test Patterns

Button Component Tests

export const ButtonInteraction: Story = {
  args: {
    onClick: fn(),
    children: 'Click me',
  },
  play: async ({ args, canvasElement }) => {
    const canvas = within(canvasElement);
    const button = canvas.getByRole('button');

    // Test rendering
    await expect(button).toBeInTheDocument();

    // Test click
    await userEvent.click(button);
    await expect(args.onClick).toHaveBeenCalledTimes(1);

    // Test disabled state
    await expect(button).not.toBeDisabled();
  },
};

Input Component Tests

export const InputInteraction: Story = {
  args: {
    label: 'Username',
    onChange: fn(),
  },
  play: async ({ args, canvasElement }) => {
    const canvas = within(canvasElement);
    const input = canvas.getByLabelText('Username');

    // Test typing
    await userEvent.type(input, 'john.doe');
    await expect(input).toHaveValue('john.doe');

    // Test change handler
    await expect(args.onChange).toHaveBeenCalled();

    // Test validation
    await userEvent.clear(input);
    await expect(input).toHaveValue('');
  },
};

Modal Component Tests

export const ModalInteraction: Story = {
  args: {
    isOpen: true,
    onClose: fn(),
    title: 'Confirm Action',
  },
  play: async ({ args, canvasElement }) => {
    const canvas = within(canvasElement);
    const dialog = canvas.getByRole('dialog');

    // Test ARIA attributes
    await expect(dialog).toHaveAttribute('aria-modal', 'true');

    // Test focus trap
    const firstButton = canvas.getAllByRole('button')[0];
    firstButton.focus();
    await expect(firstButton).toHaveFocus();

    // Test ESC key
    await userEvent.keyboard('{Escape}');
    await expect(args.onClose).toHaveBeenCalled();
  },
};

Form Component Tests

export const FormInteraction: Story = {
  args: {
    onSubmit: fn(),
  },
  play: async ({ args, canvasElement }) => {
    const canvas = within(canvasElement);

    // Fill form
    await userEvent.type(canvas.getByLabelText('Email'), 'test@example.com');
    await userEvent.type(canvas.getByLabelText('Password'), 'password123');

    // Submit
    await userEvent.click(canvas.getByRole('button', { name: /submit/i }));

    // Verify submission
    await expect(args.onSubmit).toHaveBeenCalledWith({
      email: 'test@example.com',
      password: 'password123',
    });
  },
};

Accessibility Test Patterns

WCAG 2.1 AA Compliance

export const WCAG_AA_Compliance: Story = {
  parameters: {
    a11y: {
      config: {
        rules: [
          // Perceivable
          { id: 'color-contrast', enabled: true }, // 1.4.3
          { id: 'image-alt', enabled: true }, // 1.1.1

          // Operable
          { id: 'button-name', enabled: true }, // 4.1.2
          { id: 'link-name', enabled: true }, // 4.1.2
          { id: 'focus-visible', enabled: true }, // 2.4.7

          // Understandable
          { id: 'label', enabled: true }, // 3.3.2
          { id: 'valid-lang', enabled: true }, // 3.1.1

          // Robust
          { id: 'aria-valid-attr', enabled: true }, // 4.1.2
          { id: 'aria-hidden-focus', enabled: true }, // 4.1.2
        ],
      },
    },
  },
};

Keyboard Navigation Tests

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

    // Tab through interactive elements
    await userEvent.tab();
    const firstButton = canvas.getAllByRole('button')[0];
    await expect(firstButton).toHaveFocus();

    // Activate with Enter
    await userEvent.keyboard('{Enter}');

    // Activate with Space
    await userEvent.keyboard(' ');

    // Navigate with arrows (for radio/tabs)
    await userEvent.keyboard('{ArrowRight}');
  },
};

Running Tests

Local Development

# Run all tests
npm run test-storybook

# Run specific story
npm run test-storybook -- --stories "Button/WithInteraction"

# Watch mode
npm run test-storybook -- --watch

# Debug mode
npm run test-storybook -- --debug

CI/CD Integration

Add to GitHub Actions:

name: Storybook Tests
on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: '20'

      - run: npm ci
      - run: npm run build-storybook
      - run: npm run test-storybook

Test Coverage

Storybook 9 includes V8 coverage (faster than Istanbul):

{
  "scripts": {
    "test-storybook": "test-storybook --coverage",
    "test-storybook:ci": "test-storybook --coverage --coverageReporters=lcov"
  }
}

View coverage report:

npm run test-storybook -- --coverage
# Coverage report: coverage/lcov-report/index.html

Best Practices

Do's ✅

• Use getByRole() for semantic queries
• Test user behavior, not implementation
• Keep tests focused and isolated
• Use meaningful test descriptions
• Test keyboard navigation
• Validate ARIA attributes
• Check color contrast
• Test error states

Don'ts ❌

• Don't use getByTestId() unless necessary
• Don't test internal state
• Don't duplicate tests across stories
• Don't skip accessibility tests
• Don't hardcode timeouts
• Don't ignore flaky tests

Troubleshooting

Tests Timing Out

Increase timeout in story:

export const SlowLoading: Story = {
  parameters: {
    test: {
      timeout: 10000, // 10 seconds
    },
  },
};

Elements Not Found

Use findBy queries for async elements:

const button = await canvas.findByRole('button'); // Waits up to 1s

Flaky Tests

Add explicit waits:

await waitFor(() => {
  expect(canvas.getByText('Loaded')).toBeInTheDocument();
});

Related Skills

• story-generation: Generates stories with tests automatically
• component-scaffold: Creates components with test-ready stories

References

• Storybook Testing Handbook: https://storybook.js.org/docs/writing-tests
• Testing Library Docs: https://testing-library.com/docs/queries/about
• axe-core Rules: https://github.com/dequelabs/axe-core/blob/develop/doc/rule-descriptions.md
• WCAG 2.1 Guidelines: https://www.w3.org/WAI/WCAG21/quickref/