mediar-ai/typescript-e2e-testing

E2E Testing Skill

E2E testing validates complete workflows from user perspective, using real infrastructure via Docker.

---

Workflows

For comprehensive step-by-step guidance, use the appropriate workflow:

| Workflow | When to Use | |----------|-------------| | Setup E2E Test | Setting up E2E infrastructure for a new or existing project | | Writing E2E Test | Creating new E2E test cases with proper GWT pattern | | Review E2E Test | Reviewing existing tests for quality and correctness | | Running E2E Test | Executing tests with proper verification | | Debugging E2E Test | Systematically fixing failing tests | | Optimize E2E Test | Improving test suite performance |

Workflow Selection Guide

IMPORTANT: Before starting any E2E testing task, identify the user's intent and load the appropriate workflow.

Detect User Intent → Select Workflow

| User Says / Wants | Workflow to Load | File | |-------------------|------------------|------| | "Set up E2E tests", "configure docker-compose", "add E2E to project", "create test helpers" | Setup | workflows/setup/workflow.md | | "Write E2E tests", "add integration tests", "test this endpoint", "create e2e-spec" | Writing | workflows/writing/workflow.md | | "Review E2E tests", "check test quality", "audit tests", "is this test correct?" | Reviewing | workflows/review/workflow.md | | "Run E2E tests", "execute tests", "start docker and test", "check if tests pass" | Running | workflows/running/workflow.md | | "Fix E2E tests", "debug tests", "tests are failing", "flaky test", "connection error" | Debugging | workflows/debugging/workflow.md | | "Speed up E2E tests", "optimize tests", "tests are slow", "reduce test time" | Optimizing | workflows/optimize/workflow.md |

Workflow Execution Protocol

1. ALWAYS load the workflow file first - Read the full workflow before taking action
2. Follow each step in order - Complete checkpoints before proceeding
3. Load knowledge files as directed - Each workflow specifies which references/ files to read
4. Verify compliance after completion - Re-read relevant reference files to ensure quality

Important: Each workflow includes instructions to load relevant knowledge from the references/ folder before and after completing tasks.

---

Knowledge Base Structure

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

Quick Reference by Task

Tip: For detailed step-by-step guidance, use the Workflows section above.

Setup New E2E Structure

Workflow: Setup E2E Test

1. Read references/common/knowledge.md - Understand E2E fundamentals
2. Read references/common/nestjs-setup.md - Project setup
3. Read technology-specific docker-setup.md files as needed

Write Test Cases

Workflow: Writing E2E Test

1. MANDATORY: Read references/common/rules.md - GWT pattern, timeouts
2. Read references/common/test-case-creation-guide.md - Templates
3. Read technology-specific files:
   • Kafka: references/kafka/knowledge.md → test-helper.md → isolation.md
   • PostgreSQL: references/postgres/rules.md → test-helper.md
   • MongoDB: references/mongodb/rules.md → test-helper.md
   • Redis: references/redis/rules.md → test-helper.md
   • API: references/api/rules.md → test-helper.md

Review Test Quality

Workflow: Review E2E Test

1. Read references/common/rules.md - Check against mandatory patterns
2. Read references/common/best-practices.md - Quality standards
3. Read technology-specific rules.md files

Run E2E Tests

Workflow: Running E2E Test

1. Verify Docker infrastructure is running
2. Run tests sequentially with npm run test:e2e > /tmp/e2e-${E2E_SESSION}-output.log 2>&1
3. Follow failure protocol if tests fail

Debug Failing Tests

Workflow: Debugging E2E Test

1. Read references/common/debugging.md
2. Create /tmp/e2e-${E2E_SESSION}-failures.md tracking file
3. Fix ONE test at a time

Optimize Test Performance

Workflow: Optimize E2E Test

1. Read references/common/best-practices.md - Performance patterns
2. Read references/kafka/performance.md for Kafka tests
3. Measure baseline before making changes

Examples

• Read references/common/examples.md for general patterns
• Read technology-specific examples.md for detailed scenarios

---

Core Principles

0. Context Efficiency (Temp File Output)

ALWAYS redirect E2E test output to temp files, NOT console. E2E output is verbose and bloats agent context.

IMPORTANT: Redirect output to temp files only (NO console output). Use unique session ID to prevent conflicts.

# 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

Temp Files (with ${E2E_SESSION} unique per agent):

• /tmp/e2e-${E2E_SESSION}-output.log - Full test output
• /tmp/e2e-${E2E_SESSION}-failures.log - Filtered failure output
• /tmp/e2e-${E2E_SESSION}-failures.md - Tracking file for one-by-one fixing
• /tmp/e2e-${E2E_SESSION}-debug.log - Debug runs
• /tmp/e2e-${E2E_SESSION}-verify.log - Verification runs

1. Real Infrastructure

Test against actual services via Docker. Never mock databases or message brokers for E2E tests.

2. GWT Pattern (Mandatory)

ALL E2E tests MUST follow Given-When-Then:

it('should create user and return 201', async () => {
  // GIVEN: Valid user data
  const userData = { email: '[email protected]', 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('[email protected]');
});

3. Test Isolation

Each test MUST be independent:

• Clean database state in beforeEach
• Use unique identifiers (consumer groups, topics)
• Wait for async operations to complete

4. Specific Assertions

Assert exact values, not just existence:

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

// CORRECT
expect(response.body).toMatchObject({
  code: 'SUCCESS',
  data: { email: '[email protected]', name: 'Test' }
});

---

Project Structure

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

---

Essential Jest Configuration

// 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,
};

---

Technology-Specific Timeouts

| Technology | Wait Time | Strategy | |------------|-----------|----------| | Kafka | 10-20s max (polling) | Smart polling with 50ms intervals | | PostgreSQL | <1s | Direct queries | | MongoDB | <1s | Direct queries | | Redis | <100ms | In-memory operations | | External API | 1-5s | Network latency |

---

Failure Resolution Protocol

CRITICAL: Fix ONE test at a time. NEVER run full suite repeatedly while fixing.

When E2E tests fail:

1. Initialize session (once at start):

   export E2E_SESSION=$(date +%s)-$$
   

2. Create tracking file: /tmp/e2e-${E2E_SESSION}-failures.md with all failing tests
3. Select ONE failing test - work on only this test
4. Run ONLY that test (never full suite):

   npm run test:e2e -- -t "test name" > /tmp/e2e-${E2E_SESSION}-debug.log 2>&1
   tail -50 /tmp/e2e-${E2E_SESSION}-debug.log
   

5. Fix the issue - analyze error, make targeted fix
6. Verify fix - run same test 3-5 times:

   for i in {1..5}; do npm run test:e2e -- -t "test name" > /tmp/e2e-${E2E_SESSION}-run$i.log 2>&1 && echo "Run $i: PASS" || echo "Run $i: FAIL"; done
   

7. Mark as FIXED in tracking file
8. Move to next failing test - repeat steps 3-7
9. Run full suite ONLY ONCE after ALL individual tests pass
10. Cleanup: rm -f /tmp/e2e-${E2E_SESSION}-*.log /tmp/e2e-${E2E_SESSION}-*.md

WHY: Running full suite wastes time and context. Each failing test pollutes output, making debugging harder.

---

Common Patterns

Database Cleanup (PostgreSQL/MongoDB)

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

Kafka Test Helper Pattern

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

Redis Cleanup

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

External API Mock (MSW)

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

Async Event Verification (Kafka)

// 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 });

---

Debugging Commands

All commands redirect output to temp files only (no console output).

# 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

---

Anti-Patterns to Avoid

1. Multiple WHEN actions - Split into separate tests
2. Conditional assertions - Create deterministic test cases
3. Shared state between tests - Clean in beforeEach
4. Mocking databases - Use real connections
5. Skipping cleanup - Always clean before AND after
6. Fixing multiple tests at once - Fix one at a time
7. Generic assertions - Assert specific values
8. fromBeginning: true for Kafka - Use pre-subscription + buffer clearing