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testing-library

testing-library

github.com/jezwebTesting & quality1.1k203 installsUpdated 3w ago
Repository

About testing-library

A testing guide for React developers using React Testing Library. It covers accessibility-first queries, user interactions, and asynchronous tests, with examples for mocking APIs through MSW.

Key features

  1. 01Choose queries by accessibility priority
  2. 02Simulate interactions with userEvent
  3. 03Test asynchronous UI changes
  4. 04Mock APIs with MSW
  5. 05Check accessibility issues
  6. 06Patterns for forms, dialogs, and lists

Use cases

  1. 01Verify form submission and validation
  2. 02Test asynchronous loading and dialogs
  3. 03Mock successful or failed API responses
  4. 04Check component accessibility

Install

Copy the command and run it in a terminal.

$npx skills add https://github.com/jezweb/claude-skills --skill testing-library

After installing, type/testing-libraryin Claude Code to confirm it loaded.

Bundled files

References and scripts installed along with SKILL.md.

README.md
.claude-plugin/
plugin.json
rules/
testing-library-patterns.md
templates/
msw-handlers.ts
setup.ts

Details

From the project README

React Testing Library

Status: Production Ready Last Updated: 2026-02-06 Version: 16.x User Event: 14.x


Quick Start

# Install with Vitest
pnpm add -D @testing-library/react @testing-library/user-event @testing-library/jest-dom jsdom

# Or with Jest
pnpm add -D @testing-library/react @testing-library/user-event @testing-library/jest-dom
Setup File (src/test/setup.ts)
import '@testing-library/jest-dom/vitest';
import { cleanup } from '@testing-library/react';
import { afterEach } from 'vitest';

// Cleanup after each test
afterEach(() => {
  cleanup();
});
Vitest Config
// vitest.config.ts
export default defineConfig({
  test: {
    globals: true,
    environment: 'jsdom',
    setupFiles: ['./src/test/setup.ts'],
  },
});

Query Priority (Accessibility First)

Use queries in this order for accessible, resilient tests:

PriorityQueryUse For
1getByRoleButtons, links, headings, inputs
2getByLabelTextForm inputs with labels
3getByPlaceholderTextInputs without visible labels
4getByTextNon-interactive text content
5getByTestIdLast resort only
Examples
import { render, screen } from '@testing-library/react';

// ✅ GOOD - semantic role queries
screen.getByRole('button', { name: /submit/i });
screen.getByRole('heading', { level: 1 });
screen.getByRole('textbox', { name: /email/i });
screen.getByRole('link', { name: /learn more/i });

// ✅ GOOD - label-based queries for forms
screen.getByLabelText(/email address/i);

// ⚠️ OK - when no better option
screen.getByText(/welcome to our app/i);

// ❌ AVOID - not accessible, brittle
screen.getByTestId('submit-button');

Query Variants

VariantReturnsThrowsUse For
getByElementYesElement exists now
queryByElement or nullNoElement might not exist
findByPromiseYesAsync, appears later
getAllByElement[]YesMultiple elements
queryAllByElement[]NoMultiple or none
findAllByPromise<Element[]>YesMultiple, async
When to Use Each
// Element exists immediately
const button = screen.getByRole('button');

// Check element doesn't exist
expect(screen.queryByRole('dialog')).not.toBeInTheDocument();

// Wait for async element to appear
const modal = await screen.findByRole('dialog');

// Multiple elements
const items = screen.getAllByRole('listitem');

User Event (Realistic Interactions)

Always use userEvent over fireEvent - it simulates real user behavior.

import { render, screen } from '@testing-library/react';
import userEvent from '@testing-library/user-event';

describe('Form', () => {
  it('submits form data', async () => {
    const user = userEvent.setup();
    const onSubmit = vi.fn();

    render(<LoginForm onSubmit={onSubmit} />);

    // Type in inputs
    await user.type(screen.getByLabelText(/email/i), '[email protected]');
    await user.type(screen.getByLabelText(/password/i), 'secret123');

    // Click submit
    await user.click(screen.getByRole('button', { name: /sign in/i }));

    expect(onSubmit).toHaveBeenCalledWith({
      email: '[email protected]',
      password: 'secret123',
    });
  });
});
Common User Events
const user = userEvent.setup();

// Clicking
await user.click(element);
await user.dblClick(element);
await user.tripleClick(element); // Select all text

// Typing
await user.type(input, 'hello world');
await user.clear(input);
await user.type(input, '{Enter}'); // Special keys

// Keyboard
await user.keyboard('{Shift>}A{/Shift}'); // Shift+A
await user.tab(); // Tab navigation

// Selection
await user.selectOptions(select, ['option1', 'option2']);

// Hover
await user.hover(element);
await user.unhover(element);

// Clipboard
await user.copy();
await user.paste();

Async Testing

findBy - Wait for Element
it('shows loading then content', async () => {
  render(<AsyncComponent />);

  // Shows loading initially
  expect(screen.getByText(/loading/i)).toBeInTheDocument();

  // Wait for content to appear (auto-retries)
  const content = await screen.findByText(/data loaded/i);
  expect(content).toBeInTheDocument();
});
waitFor - Wait for Condition
import { waitFor } from '@testing-library/react';

it('updates count after click', async () => {
  const user = userEvent.setup();
  render(<Counter />);

  await user.click(screen.getByRole('button', { name: /increment/i }));

  // Wait for state update
  await waitFor(() => {
    expect(screen.getByText(/count: 1/i)).toBeInTheDocument();
  });
});
waitForElementToBeRemoved
import { waitForElementToBeRemoved } from '@testing-library/react';

it('hides modal after close', async () => {
  const user = userEvent.setup();
  render(<ModalComponent />);

  await user.click(screen.getByRole('button', { name: /close/i }));

  // Wait for modal to disappear
  await waitForElementToBeRemoved(() => screen.queryByRole('dialog'));
});

MSW Integration (API Mocking)

Mock API calls at the network level with Mock Service Worker.

pnpm add -D msw
Setup (src/test/mocks/handlers.ts)
import { http, HttpResponse } from 'msw';

export const handlers = [
  http.get('/api/user', () => {
    return HttpResponse.json({
      id: 1,
      name: 'Test User',
      email: '[email protected]',
    });
  }),

  http.post('/api/login', async ({ request }) => {
    const body = await request.json();
    if (body.password === 'correct') {
      return HttpResponse.json({ token: 'abc123' });
    }
    return HttpResponse.json(
      { error: 'Invalid credentials' },
      { status: 401 }
    );
  }),
];
Setup (src/test/mocks/server.ts)
import { setupServer } from 'msw/node';
import { handlers } from './handlers';

export const server = setupServer(...handlers);
Test Setup
// src/test/setup.ts
import { server } from './mocks/server';
import { beforeAll, afterEach, afterAll } from 'vitest';

beforeAll(() => server.listen({ onUnhandledRequest: 'error' }));
afterEach(() => server.resetHandlers());
afterAll(() => server.close());
Using in Tests
import { server } from '../test/mocks/server';
import { http, HttpResponse } from 'msw';

it('handles API error', async () => {
  // Override handler for this test
  server.use(
    http.get('/api/user', () => {
      return HttpResponse.json(
        { error: 'Server error' },
        { status: 500 }
      );
    })
  );

  render(<UserProfile />);

  await screen.findByText(/error loading user/i);
});

Accessibility Testing

Check for A11y Violations
pnpm add -D @axe-core/react
import { axe, toHaveNoViolations } from 'jest-axe';

expect.extend(toHaveNoViolations);

it('has no accessibility violations', async () => {
  const { container } = render(<MyComponent />);
  const results = await axe(container);
  expect(results).toHaveNoViolations();
});
Role-Based Queries Are A11y Tests

Using getByRole implicitly tests accessibility:

// This passes only if button is properly accessible
screen.getByRole('button', { name: /submit/i });

// Fails if:
// - Element isn't a button or role="button"
// - Accessible name doesn't match
// - Element is hidden from accessibility tree

Testing Patterns

Forms
it('validates required fields', async () => {
  const user = userEvent.setup();
  render(<ContactForm />);

  // Submit without filling required fields
  await user.click(screen.getByRole('button', { name: /submit/i }));

  // Check for validation errors
  expect(screen.getByText(/email is required/i)).toBeInTheDocument();
  expect(screen.getByText(/message is required/i)).toBeInTheDocument();
});
Modals/Dialogs
it('opens and closes modal', async () => {
  const user = userEvent.setup();
  render(<ModalTrigger />);

  // Modal not visible initially
  expect(screen.queryByRole('dialog')).not.toBeInTheDocument();

  // Open modal
  await user.click(screen.getByRole('button', { name: /open/i }));
  expect(screen.getByRole('dialog')).toBeInTheDocument();

  // Close modal
  await user.click(screen.getByRole('button', { name: /close/i }));
  await waitForElementToBeRemoved(() => screen.queryByRole('dialog'));
});
Lists
it('renders list items', () => {
  render(<TodoList items={['Buy milk', 'Walk dog']} />);

  const items = screen.getAllByRole('listitem');
  expect(items).toHaveLength(2);
  expect(items[0]).toHaveTextContent('Buy milk');
});

Common Matchers (jest-dom)

// Presence
expect(element).toBeInTheDocument();
expect(element).toBeVisible();
expect(element).toBeEmptyDOMElement();

// State
expect(button).toBeEnabled();
expect(button).toBeDisabled();
expect(checkbox).toBeChecked();
expect(input).toBeRequired();

// Content
expect(element).toHaveTextContent(/hello/i);
expect(element).toHaveValue('test');
expect(element).toHaveAttribute('href', '/about');

// Styles
expect(element).toHaveClass('active');
expect(element).toHaveStyle({ color: 'red' });

// Focus
expect(input).toHaveFocus();

Debugging

screen.debug()
it('debugs rendering', () => {
  render(<MyComponent />);

  // Print entire DOM
  screen.debug();

  // Print specific element
  screen.debug(screen.getByRole('button'));
});
logRoles
import { logRoles } from '@testing-library/react';

it('shows available roles', () => {
  const { container } = render(<MyComponent />);
  logRoles(container);
});

Common Mistakes

Using getBy for Async
// ❌ WRONG - fails if element appears async
const modal = screen.getByRole('dialog');

// ✅ CORRECT - waits for element
const modal = await screen.findByRole('dialog');
Not Awaiting User Events
// ❌ WRONG - race condition
user.click(button);
expect(result).toBeInTheDocument();

// ✅ CORRECT - await the interaction
await user.click(button);
expect(result).toBeInTheDocument();
Using container.querySelector
// ❌ WRONG - not accessible, brittle
const button = container.querySelector('.submit-btn');

// ✅ CORRECT - accessible query
const button = screen.getByRole('button', { name: /submit/i });

See Also

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