[G1-Sync] Manual knowledge update

2026-05-10 22:08:15 +09:00
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+---
+id: testing-test-data-management
+title: Test Data — fixture / factory / seed / clean
+category: Coding
+status: draft
+source_trust_level: B
+verification_status: conceptual
+created_at: 2026-05-09
+updated_at: 2026-05-09
+tags: [testing, data, vibe-coding]
+tech_stack: { language: "TS / Python", applicable_to: ["Backend", "QA"] }
+applied_in: []
+aliases: [test data, fixture, factory, seed, faker, builder pattern, anonymization]
+---
+
+# Test Data Management
+
+> Test 의 가장 큰 문제 = data. **Factory + faker (random) + seed (deterministic) + clean (after)**. PII 안 사용 + repeatable.
+
+## 📖 핵심 개념
+- Fixture: 정적 data (file).
+- Factory: dynamic builder.
+- Seed: 초기 DB 상태.
+- Anonymized: prod data 의 PII 제거.
+
+## 💻 코드 패턴
+
+### Fixture (정적)
+```ts
+// fixtures/users.json
+[
+  { "id": 1, "email": "alice@test.com", "role": "admin" },
+  { "id": 2, "email": "bob@test.com", "role": "user" }
+]
+
+// 사용
+import users from './fixtures/users.json';
+beforeEach(() => db.users.insertAll(users));
+```
+
+→ 작은 / 변경 적음. 큰 = 관리 어려움.
+
+### Factory (dynamic)
+```ts
+import { faker } from '@faker-js/faker';
+
+function userFactory(overrides: Partial<User> = {}): User {
+  return {
+    id: faker.string.uuid(),
+    email: faker.internet.email(),
+    name: faker.person.fullName(),
+    age: faker.number.int({ min: 18, max: 80 }),
+    createdAt: faker.date.past(),
+    ...overrides,
+  };
+}
+
+// 사용
+const admin = userFactory({ role: 'admin' });
+const users = Array.from({ length: 10 }, () => userFactory());
+```
+
+→ 매 test 가 fresh data.
+
+### Builder pattern
+```ts
+class UserBuilder {
+  private user: Partial<User> = {};
+  
+  withEmail(e: string) { this.user.email = e; return this; }
+  withRole(r: Role) { this.user.role = r; return this; }
+  asAdmin() { this.user.role = 'admin'; return this; }
+  
+  build(): User {
+    return { ...userFactory(), ...this.user };
+  }
+}
+
+const admin = new UserBuilder().asAdmin().withEmail('a@x').build();
+```
+
+### fishery (TS factory lib)
+```ts
+import { Factory } from 'fishery';
+
+const userFactory = Factory.define<User>(({ sequence }) => ({
+  id: sequence,
+  email: `user${sequence}@test.com`,
+  name: faker.person.fullName(),
+}));
+
+const u = userFactory.build({ name: 'Alice' });
+const list = userFactory.buildList(10);
+```
+
+### factory-bot (Python)
+```python
+import factory
+
+class UserFactory(factory.Factory):
+    class Meta:
+        model = User
+    
+    id = factory.Sequence(lambda n: n)
+    email = factory.Sequence(lambda n: f'user{n}@test.com')
+    role = 'user'
+
+class AdminFactory(UserFactory):
+    role = 'admin'
+
+admin = AdminFactory()
+```
+
+### Seed (DB)
+```ts
+// seed.ts
+import { faker } from '@faker-js/faker';
+
+async function seed() {
+  // 100 user
+  const users = Array.from({ length: 100 }, () => ({
+    email: faker.internet.email(),
+    name: faker.person.fullName(),
+  }));
+  await db.users.insertAll(users);
+  
+  // 1000 order
+  const orders = Array.from({ length: 1000 }, () => ({
+    userId: faker.helpers.arrayElement(users).id,
+    amount: faker.number.int({ min: 10, max: 1000 }),
+  }));
+  await db.orders.insertAll(orders);
+}
+
+await seed();
+```
+
+→ Dev / staging 환경 초기화.
+
+### Faker faker faker
+```ts
+faker.person.fullName();           // 'Alice Johnson'
+faker.internet.email();            // 'alice@example.com'
+faker.location.city();             // 'New York'
+faker.commerce.productName();      // 'Laptop'
+faker.number.int({ min: 1, max: 100 });
+faker.date.recent();
+faker.lorem.paragraphs(3);
+faker.image.url();
+faker.string.uuid();
+```
+
+→ Locale 가능: `faker.locale = 'ko'`.
+
+### Determinism
+```ts
+faker.seed(42);
+const u1 = faker.person.fullName();  // 항상 같은 결과
+
+// Sequence
+let _id = 0;
+function nextId() { return _id++; }
+```
+
+→ Test 가 reproducible.
+
+### Reset (테스트 격리)
+```ts
+afterEach(async () => {
+  await db.query('TRUNCATE users, orders CASCADE');
+});
+
+// 또는 transaction rollback
+beforeEach(async () => {
+  await db.query('BEGIN');
+});
+afterEach(async () => {
+  await db.query('ROLLBACK');
+});
+```
+
+→ 매 test 가 깨끗.
+
+### Snapshot DB
+```bash
+# Reset 빠른 방법
+pg_dump test_db > snapshot.sql
+
+# 매 test
+dropdb test_db && createdb test_db && psql test_db < snapshot.sql
+```
+
+→ 큰 seed 가 매번 다시 X.
+
+### Testcontainers
+```ts
+import { PostgreSqlContainer } from '@testcontainers/postgresql';
+
+beforeAll(async () => {
+  pg = await new PostgreSqlContainer().start();
+  await runMigrations(pg.getConnectionUri());
+  await seed();
+});
+
+afterAll(() => pg.stop());
+```
+
+→ Docker container 가 test 시작/종료.
+
+### Production data anonymization
+```sql
+-- Prod → staging dump
+UPDATE users SET
+  email = 'user' || id || '@test.com',
+  phone = '000-0000-0000',
+  ssn = NULL,
+  full_name = 'User ' || id;
+
+DELETE FROM payment_methods;
+DELETE FROM messages WHERE created_at < NOW() - INTERVAL '30 days';
+```
+
+→ PII / payment 제거.
+
+### Synthetic prod data
+```python
+# Prod 의 분포 학습 → fake 생성
+from sdv.tabular import GaussianCopula
+
+model = GaussianCopula()
+model.fit(prod_users_df)
+fake_users = model.sample(10000)
+```
+
+→ [[AI_Synthetic_Data]].
+
+### 마스킹 vs 가짜 vs 합성
+```
+Masking: 기존 → blur (Alice → A*****)
+Faker: 새 random
+Synthetic: 분포 보존 + 새
+
+→ 통계 분석 = synthetic.
+일반 test = faker.
+```
+
+### Time travel
+```ts
+// 시간 의존 test
+import MockDate from 'mockdate';
+MockDate.set('2026-05-09T00:00:00Z');
+
+// ... test ...
+
+afterEach(() => MockDate.reset());
+```
+
+### UUID 의 함정
+```ts
+// ❌ 매 test 가 다른 UUID = snapshot 깨짐
+const u = { id: faker.string.uuid() };
+expect(u).toMatchSnapshot();
+
+// ✅ Fixed
+const u = { id: '00000000-0000-0000-0000-000000000001' };
+```
+
+### Test data 공유 (shared)
+```
+beforeAll = 모든 test 공유.
+beforeEach = 매 test fresh.
+
+→ Read-only test = beforeAll OK.
+Write test = beforeEach 필수 (격리).
+```
+
+### Builder 의 약점
+```
+큰 entity = builder 길음:
+new UserBuilder()
+  .withName(...)
+  .withEmail(...)
+  .withRole(...)
+  .withAddress(...)
+  .build();
+
+→ Default 가 좋고 + override 만 나은 경우 많음.
+```
+
+→ Factory + override ({...}) 가 ergonomic.
+
+### Test 의 data dependency
+```
+"이 user 가 있어야 X" → setup.
+"이 order 가 있어야 Y" → setup + relation.
+"이 user + order 합 = Z" → 복잡 setup.
+
+→ Builder / factory 가 도움.
+```
+
+### Idempotent seed
+```ts
+async function seedIdempotent() {
+  const exists = await db.users.findOne({ email: 'admin@x.com' });
+  if (!exists) {
+    await db.users.insert({ email: 'admin@x.com', ... });
+  }
+}
+```
+
+→ 다시 실행 OK.
+
+### CI 의 data
+```
+CI 가 매번 새 DB / container.
+- Migration 실행
+- Seed 실행
+- Test 실행
+
+→ Hermetic.
+```
+
+### Performance test data
+```
+큰 양 (100k user, 1M order):
+- Bulk insert (COPY in postgres)
+- Generate file → load
+- 매 test 가 X
+
+bulk_insert(users, 100_000)  # 빠름
+```
+
+### 함정: Test 가 prod data 가정
+```ts
+// ❌ "user_id 1 가 항상 admin" 가정
+test('admin can delete', () => {
+  ...
+});
+
+// ✅ 매 test 가 admin 명시 생성
+test('admin can delete', () => {
+  const admin = userFactory({ role: 'admin' });
+  ...
+});
+```
+
+### Fixtures vs factory
+```
+Fixture:
+- 작은 / 정적 / shared
+- "전형적 user 5명"
+
+Factory:
+- Dynamic / parameter
+- "임의 admin / banned user"
+
+→ 둘 다 함께 가능.
+```
+
+## 🤔 의사결정 기준
+| 작업 | 추천 |
+|---|---|
+| 단순 unit test | Factory (fishery / factory-bot) |
+| Integration test | Factory + DB seed |
+| E2E test | Docker + 큰 seed |
+| Big data | Bulk insert + snapshot |
+| 시간 의존 | MockDate |
+| Snapshot test | Fixed (no UUID) |
+| Prod 가까움 | Anonymized / synthetic |
+
+## ❌ 안티패턴
+- **Test 가 prod data 가정**: fragile.
+- **모든 test 가 1 fixture**: 격리 X.
+- **PII in test**: 누출 가능.
+- **Cleanup 없음**: 다음 test 영향.
+- **Faker 가 결정 X**: snapshot 깨짐.
+- **Fixture 거대 (10MB+)**: 관리 X.
+- **Seed 가 idempotent X**: 재실행 깨짐.
+
+## 🤖 LLM 활용 힌트
+- Factory + faker = ergonomic.
+- 매 test 가 격리 (clean / transaction).
+- Prod-like = anonymized / synthetic.
+- Determinism (seed) = reproducible.
+
+## 🔗 관련 문서
+- [[Testing_Faker_and_Builders]]
+- [[AI_Synthetic_Data]]
+- [[DB_Migration_Safety]]