trackgo-be/.agents/skills/tdd-workflow/SKILL.md

---
name: tdd-workflow
description: Use this skill when writing new features, fixing bugs, or refactoring code. Enforces test-driven development with 80%+ coverage including unit, integration, and E2E tests.
---

# Test-Driven Development Workflow

This skill ensures all code development follows TDD principles with comprehensive test coverage.

## When to Activate

- Writing new features or functionality
- Fixing bugs or issues
- Refactoring existing code
- Adding API endpoints
- Creating new components

## Core Principles

### 1. Tests BEFORE Code
ALWAYS write tests first, then implement code to make tests pass.

### 2. Coverage Requirements
- Minimum 80% coverage (unit + integration + E2E)
- All edge cases covered
- Error scenarios tested
- Boundary conditions verified

### 3. Test Types

#### Unit Tests
- Individual functions and utilities
- Component logic
- Pure functions
- Helpers and utilities

#### Integration Tests
- API endpoints
- Database operations
- Service interactions
- External API calls

#### E2E Tests (Supertest)
- Critical API flows
- Complete HTTP workflows
- Auth, validation, and error responses

## TDD Workflow Steps

### Step 1: Write User Journeys
```
As a [role], I want to [action], so that [benefit]

Example:
As a user, I want to search for markets semantically,
so that I can find relevant markets even without exact keywords.
```

### Step 2: Generate Test Cases
For each user journey, create comprehensive test cases:

```typescript
describe('Semantic Search', () => {
  it('returns relevant markets for query', async () => {
    // Test implementation
  })

  it('handles empty query gracefully', async () => {
    // Test edge case
  })

  it('falls back to substring search when Redis unavailable', async () => {
    // Test fallback behavior
  })

  it('sorts results by similarity score', async () => {
    // Test sorting logic
  })
})
```

### Step 3: Run Tests (They Should Fail)
```bash
npm test
# Tests should fail - we haven't implemented yet
```

### Step 4: Implement Code
Write minimal code to make tests pass:

```typescript
// Implementation guided by tests
export async function searchMarkets(query: string) {
  // Implementation here
}
```

### Step 5: Run Tests Again
```bash
npm test
# Tests should now pass
```

### Step 6: Refactor
Improve code quality while keeping tests green:
- Remove duplication
- Improve naming
- Optimize performance
- Enhance readability

### Step 7: Verify Coverage
```bash
npm run test:coverage
# Verify 80%+ coverage achieved
```

## Testing Patterns

### Unit Test Pattern (Jest/Vitest)
```typescript
import { render, screen, fireEvent } from '@testing-library/react'
import { Button } from './Button'

describe('Button Component', () => {
  it('renders with correct text', () => {
    render(<Button>Click me</Button>)
    expect(screen.getByText('Click me')).toBeInTheDocument()
  })

  it('calls onClick when clicked', () => {
    const handleClick = jest.fn()
    render(<Button onClick={handleClick}>Click</Button>)

    fireEvent.click(screen.getByRole('button'))

    expect(handleClick).toHaveBeenCalledTimes(1)
  })

  it('is disabled when disabled prop is true', () => {
    render(<Button disabled>Click</Button>)
    expect(screen.getByRole('button')).toBeDisabled()
  })
})
```

### API Integration Test Pattern
```typescript
import { NextRequest } from 'next/server'
import { GET } from './route'

describe('GET /api/markets', () => {
  it('returns markets successfully', async () => {
    const request = new NextRequest('http://localhost/api/markets')
    const response = await GET(request)
    const data = await response.json()

    expect(response.status).toBe(200)
    expect(data.success).toBe(true)
    expect(Array.isArray(data.data)).toBe(true)
  })

  it('validates query parameters', async () => {
    const request = new NextRequest('http://localhost/api/markets?limit=invalid')
    const response = await GET(request)

    expect(response.status).toBe(400)
  })

  it('handles database errors gracefully', async () => {
    // Mock database failure
    const request = new NextRequest('http://localhost/api/markets')
    // Test error handling
  })
})
```

### E2E Test Pattern (Supertest)
```typescript
import { INestApplication } from '@nestjs/common'
import { Test } from '@nestjs/testing'
import request from 'supertest'
import { AppModule } from '../src/app.module'

describe('Users (e2e)', () => {
  let app: INestApplication

  beforeAll(async () => {
    const moduleRef = await Test.createTestingModule({
      imports: [AppModule],
    }).compile()

    app = moduleRef.createNestApplication()
    await app.init()
  })

  afterAll(async () => {
    await app.close()
  })

  it('POST /users creates a user', async () => {
    await request(app.getHttpServer())
      .post('/users')
      .send({ email: 'ada@example.com', password: 'secret123' })
      .expect(201)
  })
})
```

## Test File Organization

```
src/
└── modules/
    └── users/
        ├── users.module.ts
        ├── users.controller.ts
        ├── users.controller.spec.ts   # Unit tests
        ├── users.service.ts
        ├── users.service.spec.ts
        └── dto/
test/
├── jest-e2e.json
├── app.e2e-spec.ts                    # E2E tests
└── users.e2e-spec.ts
```

## Mocking External Services

### Drizzle Mock
```typescript
const db = {
  query: {
    users: {
      findFirst: jest.fn(),
      findMany: jest.fn(),
    },
  },
  insert: jest.fn(),
  update: jest.fn(),
  delete: jest.fn(),
}
```

### Redis Mock
```typescript
jest.mock('@/lib/redis', () => ({
  searchMarketsByVector: jest.fn(() => Promise.resolve([
    { slug: 'test-market', similarity_score: 0.95 }
  ])),
  checkRedisHealth: jest.fn(() => Promise.resolve({ connected: true }))
}))
```

### OpenAI Mock
```typescript
jest.mock('@/lib/openai', () => ({
  generateEmbedding: jest.fn(() => Promise.resolve(
    new Array(1536).fill(0.1) // Mock 1536-dim embedding
  ))
}))
```

## Test Coverage Verification

### Run Coverage Report
```bash
npm run test:coverage
```

### Coverage Thresholds
```json
{
  "jest": {
    "coverageThresholds": {
      "global": {
        "branches": 80,
        "functions": 80,
        "lines": 80,
        "statements": 80
      }
    }
  }
}
```

## Common Testing Mistakes to Avoid

### ❌ WRONG: Testing Implementation Details
```typescript
// Don't test internal state
expect(component.state.count).toBe(5)
```

### ✅ CORRECT: Test User-Visible Behavior
```typescript
// Test what users see
expect(screen.getByText('Count: 5')).toBeInTheDocument()
```

### ❌ WRONG: Brittle Selectors
```typescript
// Breaks easily
await page.click('.css-class-xyz')
```

### ✅ CORRECT: Semantic Selectors
```typescript
// Resilient to changes
await page.click('button:has-text("Submit")')
await page.click('[data-testid="submit-button"]')
```

### ❌ WRONG: No Test Isolation
```typescript
// Tests depend on each other
test('creates user', () => { /* ... */ })
test('updates same user', () => { /* depends on previous test */ })
```

### ✅ CORRECT: Independent Tests
```typescript
// Each test sets up its own data
test('creates user', () => {
  const user = createTestUser()
  // Test logic
})

test('updates user', () => {
  const user = createTestUser()
  // Update logic
})
```

## Continuous Testing

### Watch Mode During Development
```bash
npm test -- --watch
# Tests run automatically on file changes
```

### Pre-Commit Hook
```bash
# Runs before every commit
npm test && npm run lint
```

### CI/CD Integration
```yaml
# GitHub Actions
- name: Run Tests
  run: npm test -- --coverage
- name: Upload Coverage
  uses: codecov/codecov-action@v3
```

## Best Practices

1. **Write Tests First** - Always TDD
2. **One Assert Per Test** - Focus on single behavior
3. **Descriptive Test Names** - Explain what's tested
4. **Arrange-Act-Assert** - Clear test structure
5. **Mock External Dependencies** - Isolate unit tests
6. **Test Edge Cases** - Null, undefined, empty, large
7. **Test Error Paths** - Not just happy paths
8. **Keep Tests Fast** - Unit tests < 50ms each
9. **Clean Up After Tests** - No side effects
10. **Review Coverage Reports** - Identify gaps

## Success Metrics

- 80%+ code coverage achieved
- All tests passing (green)
- No skipped or disabled tests
- Fast test execution (< 30s for unit tests)
- E2E tests cover critical user flows
- Tests catch bugs before production

---

**Remember**: Tests are not optional. They are the safety net that enables confident refactoring, rapid development, and production reliability.