react-testing

React Testing Patterns

Test framework selection

Match what's installed. Vitest is the modern default for Vite projects; Jest is common in CRA / older setups.

Vitest setup

vitest.config.ts:

import { defineConfig } from 'vitest/config';
import react from '@vitejs/plugin-react';
import path from 'path';

export default defineConfig({
  plugins: [react()],
  test: {
    environment: 'jsdom',
    globals: true,
    setupFiles: ['./vitest.setup.ts'],
    css: true,
    coverage: {
      reporter: ['text', 'html'],
      exclude: ['**/*.config.*', '**/*.test.*', 'src/main.tsx'],
    },
  },
  resolve: {
    alias: { '@': path.resolve(__dirname, './src') },
  },
});

vitest.setup.ts:

import '@testing-library/jest-dom/vitest';
import { afterEach } from 'vitest';
import { cleanup } from '@testing-library/react';

afterEach(() => cleanup());

Install: pnpm add -D vitest @vitejs/plugin-react jsdom @testing-library/react @testing-library/user-event @testing-library/jest-dom.

Jest setup

jest.config.ts:

import type { Config } from 'jest';

const config: Config = {
  preset: 'ts-jest',
  testEnvironment: 'jsdom',
  setupFilesAfterEach: ['<rootDir>/jest.setup.ts'],
  moduleNameMapper: {
    '^@/(.*)$': '<rootDir>/src/$1',
    '\\.(css|scss|less)$': 'identity-obj-proxy',
  },
};
export default config;

jest.setup.ts:

import '@testing-library/jest-dom';

Component test (RTL basics)

// src/features/users/UserCard.test.tsx
import { describe, it, expect } from 'vitest';
import { render, screen } from '@testing-library/react';
import userEvent from '@testing-library/user-event';
import { UserCard } from './UserCard';

describe('UserCard', () => {
  it('renders user name and email', () => {
    render(<UserCard user={{ id: '1', name: 'Alice', email: '[email protected]' }} />);
    expect(screen.getByRole('heading', { name: 'Alice' })).toBeInTheDocument();
    expect(screen.getByText('[email protected]')).toBeInTheDocument();
  });

  it('calls onDelete when delete button clicked', async () => {
    const onDelete = vi.fn();
    const user = userEvent.setup();
    render(<UserCard user={{ id: '1', name: 'Alice', email: '[email protected]' }} onDelete={onDelete} />);
    await user.click(screen.getByRole('button', { name: /delete/i }));
    expect(onDelete).toHaveBeenCalledWith('1');
  });
});