javascript-testing-patterns

Erwartetes Ergebnis:

• ```typescript
• import { describe, it, expect } from 'vitest';
• import { add } from './calculator';
•  
• describe('add', () => {
• it('should add two positive numbers', () => {
• expect(add(2, 3)).toBe(5);
• });
•  
• it('should add negative numbers', () => {
• expect(add(-2, -3)).toBe(-5);
• });
•  
• it('should handle zero', () => {
• expect(add(0, 5)).toBe(5);
• });
• });
• ```

Erwartetes Ergebnis:

• ```typescript
• import { render, screen, fireEvent } from '@testing-library/react';
• import { describe, it, expect, vi } from 'vitest';
• import { UserForm } from './UserForm';
•  
• describe('UserForm', () => {
• it('should show validation error for invalid email', () => {
• render(<UserForm onSubmit={vi.fn()} />);
• fireEvent.change(screen.getByTestId('email-input'), {
• target: { value: 'invalid-email' }
• });
• fireEvent.click(screen.getByRole('button', { name: 'Submit' }));
• expect(screen.getByText('Invalid email')).toBeInTheDocument();
• });
•  
• it('should call onSubmit with form data', () => {
• const onSubmit = vi.fn();
• render(<UserForm onSubmit={onSubmit} />);
• fireEvent.change(screen.getByTestId('name-input'), {
• target: { value: 'John Doe' }
• });
• fireEvent.change(screen.getByTestId('email-input'), {
• target: { value: 'john@example.com' }
• });
• fireEvent.click(screen.getByRole('button', { name: 'Submit' }));
• expect(onSubmit).toHaveBeenCalledWith({
• name: 'John Doe',
• email: 'john@example.com'
• });
• });
• });
• ```