Testing NestJS Applications

When to use

• Writing tests for use cases, controllers, or full HTTP flows
• Setting up test strategy for a NestJS feature
• Replacing mocks with hand-rolled fakes

Core rules

1. Unit tests: domain entities with pure assertions (no NestJS testing module)
2. Use-cases tested with hand-rolled fakes (not jest.mock)
3. Integration tests: Test.createTestingModule with real or fake providers
4. E2E tests: Supertest against bootstrapped app
5. No jest.mock for internal modules; only for third-party if needed

Reference shape (TypeScript)

Unit Test (Domain Entity)

import { User } from './user.entity';