TypeScriptsrc/notification.test.ts
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import { describe, it, expect, vi, beforeEach } from 'vitest';
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// Module mock — replaces entire module
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vi.mock('./mailer', () => ({
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  sendEmail: vi.fn(),
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  sendSMS: vi.fn(),
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}));
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import { sendEmail, sendSMS } from './mailer';
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import { NotificationService } from './notification-service';
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describe('NotificationService', () => {
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  let service: NotificationService;
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  beforeEach(() => {
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    vi.clearAllMocks();  // Reset call history, keep mock implementations
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    service = new NotificationService();
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  });
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  it('sends email notification', async () => {
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    vi.mocked(sendEmail).mockResolvedValue({ messageId: 'msg-1' });
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    await service.notifyUser({
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      userId: 'u-1',
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      type: 'welcome',
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      email: 'alice@example.com',
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    });
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    expect(sendEmail).toHaveBeenCalledWith({
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      to: 'alice@example.com',
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      subject: expect.stringContaining('Welcome'),
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      html: expect.any(String),
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    });
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    expect(sendEmail).toHaveBeenCalledOnce();
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  });
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  it('retries on failure then succeeds', async () => {
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    vi.mocked(sendEmail)
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      .mockRejectedValueOnce(new Error('SMTP timeout'))
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      .mockResolvedValueOnce({ messageId: 'msg-2' });  // Second call succeeds
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    await service.notifyUser({
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      userId: 'u-2',
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      type: 'password-reset',
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      email: 'bob@example.com',
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    });
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    expect(sendEmail).toHaveBeenCalledTimes(2);  // Retried once
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  });
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  it('throws after max retries exhausted', async () => {
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    vi.mocked(sendEmail).mockRejectedValue(new Error('SMTP down'));
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    await expect(
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      service.notifyUser({ userId: 'u-3', type: 'welcome', email: 'x@x.com' })
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    ).rejects.toThrow('Failed to send notification after 3 attempts');
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    expect(sendEmail).toHaveBeenCalledTimes(3);
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  });
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});
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// Minimal NotificationService for test
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class NotificationService {
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  async notifyUser(payload: { userId: string; type: string; email: string }) {
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    const maxRetries = 3;
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    for (let attempt = 0; attempt < maxRetries; attempt++) {
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      try {
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        await sendEmail({
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          to: payload.email,
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          subject: `Welcome to our app`,
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          html: `<p>Hi!</p>`,
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        });
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        return;
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      } catch (err) {
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        if (attempt === maxRetries - 1) {
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          throw new Error(`Failed to send notification after ${maxRetries} attempts`);
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        }
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      }
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    }
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  }
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}