references/
├── common/              # Shared testing fundamentals
│   ├── knowledge.md     # Core E2E concepts and test pyramid
│   ├── rules.md         # Mandatory testing rules (GWT, timeouts, logging)
│   ├── best-practices.md # Test design and cleanup patterns
│   ├── test-case-creation-guide.md # GWT templates for all scenarios
│   ├── nestjs-setup.md  # NestJS app bootstrap and Jest config
│   ├── debugging.md     # VS Code config and log analysis
│   └── examples.md      # Comprehensive examples by category
│
├── kafka/               # Kafka-specific testing
│   ├── knowledge.md     # Why common approaches fail, architecture
│   ├── rules.md         # Kafka-specific testing rules
│   ├── test-helper.md   # KafkaTestHelper implementation
│   ├── docker-setup.md  # Redpanda/Kafka Docker configs
│   ├── performance.md   # Optimization techniques
│   ├── isolation.md     # Pre-subscription pattern details
│   └── examples.md      # Kafka test examples
│
├── postgres/            # PostgreSQL-specific testing
│   ├── knowledge.md     # PostgreSQL testing concepts
│   ├── rules.md         # Cleanup, transaction, assertion rules
│   ├── test-helper.md   # PostgresTestHelper implementation
│   └── examples.md      # CRUD, transaction, constraint examples
│
├── mongodb/             # MongoDB-specific testing
│   ├── knowledge.md     # MongoDB testing concepts
│   ├── rules.md         # Document cleanup and assertion rules
│   ├── test-helper.md   # MongoDbTestHelper implementation
│   ├── docker-setup.md  # Docker and Memory Server setup
│   └── examples.md      # Document and aggregation examples
│
├── redis/               # Redis-specific testing
│   ├── knowledge.md     # Redis testing concepts
│   ├── rules.md         # TTL and pub/sub rules
│   ├── test-helper.md   # RedisTestHelper implementation
│   ├── docker-setup.md  # Docker configuration
│   └── examples.md      # Cache, session, rate limit examples
│
└── api/                 # API testing (REST, GraphQL, gRPC)
    ├── knowledge.md     # API testing concepts
    ├── rules.md         # Request/response assertion rules
    ├── test-helper.md   # Auth and Supertest helpers
    ├── examples.md      # REST, GraphQL, validation examples
    └── mocking.md       # MSW and Nock external API mocking

# Generate unique session ID at start of debugging session
export E2E_SESSION=$(date +%s)-$$

# Standard pattern - redirect to file only (no console output)
npm run test:e2e > /tmp/e2e-${E2E_SESSION}-output.log 2>&1

# Read summary only (last 50 lines)
tail -50 /tmp/e2e-${E2E_SESSION}-output.log

# Get failure details
grep -B 2 -A 15 "FAIL\|✕" /tmp/e2e-${E2E_SESSION}-output.log

# Cleanup when done
rm -f /tmp/e2e-${E2E_SESSION}-*.log /tmp/e2e-${E2E_SESSION}-*.md

it('should create user and return 201', async () => {
  // GIVEN: Valid user data
  const userData = { email: 'test@example.com', name: 'Test' };

  // WHEN: Creating user
  const response = await request(httpServer)
    .post('/users')
    .send(userData)
    .expect(201);

  // THEN: User created with correct data
  expect(response.body.data.email).toBe('test@example.com');
});

// WRONG
expect(response.body.data).toBeDefined();

// CORRECT
expect(response.body).toMatchObject({
  code: 'SUCCESS',
  data: { email: 'test@example.com', name: 'Test' }
});

project-root/
├── src/
├── test/
│   ├── e2e/
│   │   ├── feature.e2e-spec.ts
│   │   ├── setup.ts
│   │   └── helpers/
│   │       ├── test-app.helper.ts
│   │       ├── postgres.helper.ts
│   │       ├── mongodb.helper.ts
│   │       ├── redis.helper.ts
│   │       └── kafka.helper.ts
│   └── jest-e2e.config.ts
├── docker-compose.e2e.yml
├── .env.e2e
└── package.json

// test/jest-e2e.config.ts
const config: Config = {
  preset: 'ts-jest',
  testEnvironment: 'node',
  testMatch: ['**/*.e2e-spec.ts'],
  testTimeout: 25000,
  maxWorkers: 1,           // CRITICAL: Sequential execution
  clearMocks: true,
  forceExit: true,
  detectOpenHandles: true,
};

beforeEach(async () => {
  await new Promise(r => setTimeout(r, 500)); // Wait for in-flight
  await repository.clear();  // PostgreSQL
  // OR
  await model.deleteMany({}); // MongoDB
});

// Use pre-subscription + buffer clearing (NOT fromBeginning: true)
const kafkaHelper = new KafkaTestHelper();
await kafkaHelper.subscribeToTopic(outputTopic, false);
// In beforeEach: kafkaHelper.clearMessages(outputTopic);

beforeEach(async () => {
  await redis.flushdb();
});

mockServer.use(
  http.post('https://api.external.com/endpoint', () => {
    return HttpResponse.json({ status: 'success' });
  })
);

// Use smart polling instead of fixed waits
await kafkaHelper.publishEvent(inputTopic, event, event.id);
const messages = await kafkaHelper.waitForMessages(outputTopic, 1, 20000);
expect(messages[0].value).toMatchObject({ id: event.id });

# Initialize session (once at start)
export E2E_SESSION=$(date +%s)-$$

# Run specific test (no console output)
npm run test:e2e -- -t "should create user" > /tmp/e2e-${E2E_SESSION}-output.log 2>&1 && tail -50 /tmp/e2e-${E2E_SESSION}-output.log

# Run specific file
npm run test:e2e -- test/e2e/user.e2e-spec.ts > /tmp/e2e-${E2E_SESSION}-output.log 2>&1 && tail -50 /tmp/e2e-${E2E_SESSION}-output.log

# Run full suite
npm run test:e2e > /tmp/e2e-${E2E_SESSION}-output.log 2>&1 && tail -50 /tmp/e2e-${E2E_SESSION}-output.log

# Get failure details from last run
grep -B 2 -A 15 "FAIL\|✕" /tmp/e2e-${E2E_SESSION}-output.log

# Debug with breakpoints (requires console for interactive debugging)
node --inspect-brk node_modules/.bin/jest --config test/jest-e2e.config.ts --runInBand

# View application logs (limited)
tail -100 logs/e2e-test.log
grep -i error logs/e2e-test.log | tail -50

# Cleanup session files
rm -f /tmp/e2e-${E2E_SESSION}-*.log /tmp/e2e-${E2E_SESSION}-*.md