test-driven-development

Ожидаемый результат:

• RED: Writing failing test first
• test('rejects empty email with error message', async () => {
• const result = await login({ email: '', password: 'password123' });
• expect(result.error).toBe('Email required');
• });
•  
• GREEN: Minimal implementation to pass test
• function login(data) {
• if (!data.email?.trim()) {
• return { error: 'Email required' };
• }
• // ... rest of login logic
• }
•  
• Next test: Add password validation, then continue the cycle.

Ожидаемый результат:

• RED: First failing test
• test('retries failed operations 3 times', async () => {
• let attempts = 0;
• const operation = () => {
• attempts++;
• if (attempts < 3) throw new Error('fail');
• return 'success';
• };
• const result = await retryOperation(operation);
• expect(result).toBe('success');
• expect(attempts).toBe(3);
• });
•  
• GREEN: Minimal code to pass
• async function retryOperation(fn) {
• for (let i = 0; i < 3; i++) {
• try { return await fn(); }
• catch (e) { if (i === 2) throw e; }
• }
• }