Node.js 테스팅 전략 — 단위, 통합, E2E 테스트

npm install -D vitest @vitest/coverage-v8 supertest

// vitest.config.ts
import { defineConfig } from 'vitest/config';

export default defineConfig({
  test: {
    environment: 'node',
    globals: true,
    coverage: {
      provider: 'v8',
      reporter: ['text', 'lcov'],
      exclude: ['node_modules', 'dist', '**/*.d.ts'],
    },
  },
});

// src/utils/formatDate.ts
export function formatDate(date: Date, locale = 'ko-KR'): string {
  return new Intl.DateTimeFormat(locale, {
    year: 'numeric',
    month: 'long',
    day: 'numeric',
  }).format(date);
}

// src/utils/formatDate.test.ts
import { describe, it, expect } from 'vitest';
import { formatDate } from './formatDate';

describe('formatDate', () => {
  it('한국어 날짜 형식으로 변환한다', () => {
    const date = new Date('2024-01-15');
    expect(formatDate(date)).toBe('2024년 1월 15일');
  });

  it('영어 형식도 지원한다', () => {
    const date = new Date('2024-01-15');
    expect(formatDate(date, 'en-US')).toMatch(/January 15, 2024/);
  });
});

// tests/users.test.ts
import { describe, it, expect, beforeAll, afterAll } from 'vitest';
import request from 'supertest';
import { app } from '../src/app';
import { prisma } from '../src/lib/prisma';

beforeAll(async () => {
  await prisma.$executeRaw`DELETE FROM users WHERE email LIKE '%@test.com'`;
});

afterAll(async () => {
  await prisma.$disconnect();
});

describe('POST /api/users', () => {
  it('유효한 데이터로 유저를 생성한다', async () => {
    const res = await request(app)
      .post('/api/users')
      .send({ email: 'test@test.com', name: '테스트' })
      .expect(201);

    expect(res.body).toMatchObject({ email: 'test@test.com' });
    expect(res.body.id).toBeDefined();
  });

  it('이메일 없으면 400을 반환한다', async () => {
    await request(app)
      .post('/api/users')
      .send({ name: '테스트' })
      .expect(400);
  });
});

import { vi, describe, it, expect } from 'vitest';
import { sendEmail } from '../src/services/email';

vi.mock('../src/services/email', () => ({
  sendEmail: vi.fn().mockResolvedValue({ id: 'mock-123' }),
}));

it('주문 생성 시 이메일을 발송한다', async () => {
  await orderService.createOrder({ userId: 1, items: [] });
  expect(sendEmail).toHaveBeenCalledWith(
    expect.objectContaining({ subject: '주문 확인' })
  );
});

it('API 응답 구조가 변경되지 않는다', async () => {
  const res = await request(app).get('/api/config').expect(200);
  expect(res.body).toMatchSnapshot();
});

{
  "scripts": {
    "test": "vitest run",
    "test:coverage": "vitest run --coverage --coverage.thresholds.statements=80"
  }
}