Testing

import { describe, it, expect } from 'vitest';
import { add, multiply } from './math';

describe('math utilities', () => {
  it('adds two numbers', () => {
    expect(add(2, 3)).toBe(5);
  });

  it('multiplies two numbers', () => {
    expect(multiply(4, 5)).toBe(20);
  });
});

import { render, screen, fireEvent } from '@testing-library/react';
import { Button } from './Button';

describe('Button', () => {
  it('renders with text', () => {
    render(<Button>Click me</Button>);
    expect(screen.getByText('Click me')).toBeInTheDocument();
  });

  it('calls onClick when clicked', () => {
    const handleClick = vi.fn();
    render(<Button onClick={handleClick}>Click</Button>);

    fireEvent.click(screen.getByText('Click'));
    expect(handleClick).toHaveBeenCalledOnce();
  });
});

import { vi } from 'vitest';

// Mock a module
vi.mock('./api', () => ({
  fetchUser: vi.fn(() => Promise.resolve({ id: 1, name: 'John' })),
}));

// Mock a function
const mockFn = vi.fn();
mockFn.mockReturnValue(42);