tdd-workflow

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

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 (Playwright)

• Critical user flows
• Complete workflows
• Browser automation
• UI interactions

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

```

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(Click me)

expect(screen.getByText('Click me')).toBeInTheDocument()

})

it('calls onClick when clicked', () => {

const handleClick = jest.fn()

render(Click)

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

expect(handleClick).toHaveBeenCalledTimes(1)

})

it('is disabled when disabled prop is true', () => {

render(Click)

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 (Playwright)

```typescript

import { test, expect } from '@playwright/test'

test('user can search and filter markets', async ({ page }) => {

// Navigate to markets page

await page.goto('/')

await page.click('a[href="/markets"]')

// Verify page loaded

await expect(page.locator('h1')).toContainText('Markets')

// Search for markets

await page.fill('input[placeholder="Search markets"]', 'election')

// Wait for debounce and results

await page.waitForTimeout(600)

// Verify search results displayed

const results = page.locator('[data-testid="market-card"]')

await expect(results).toHaveCount(5, { timeout: 5000 })

// Verify results contain search term

const firstResult = results.first()

await expect(firstResult).toContainText('election', { ignoreCase: true })

// Filter by status

await page.click('button:has-text("Active")')

// Verify filtered results

await expect(results).toHaveCount(3)

})

test('user can create a new market', async ({ page }) => {

// Login first

await page.goto('/creator-dashboard')

// Fill market creation form

await page.fill('input[name="name"]', 'Test Market')

await page.fill('textarea[name="description"]', 'Test description')

await page.fill('input[name="endDate"]', '2025-12-31')

// Submit form

await page.click('button[type="submit"]')

// Verify success message

await expect(page.locator('text=Market created successfully')).toBeVisible()

// Verify redirect to market page

await expect(page).toHaveURL(/\/markets\/test-market/)

})

```

```

src/

├── components/

│ ├── Button/

│ │ ├── Button.tsx

│ │ ├── Button.test.tsx # Unit tests

│ │ └── Button.stories.tsx # Storybook

│ └── MarketCard/

│ ├── MarketCard.tsx

│ └── MarketCard.test.tsx

├── app/

│ └── api/

│ └── markets/

│ ├── route.ts

│ └── route.test.ts # Integration tests

└── e2e/

├── markets.spec.ts # E2E tests

├── trading.spec.ts

└── auth.spec.ts

```

Supabase Mock

```typescript

jest.mock('@/lib/supabase', () => ({

supabase: {

from: jest.fn(() => ({

select: jest.fn(() => ({

eq: jest.fn(() => Promise.resolve({

data: [{ id: 1, name: 'Test Market' }],

error: null

}))

}))

}))

}

}))

```

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

))

}))

```

Run Coverage Report

```bash

npm run test:coverage

```

Coverage Thresholds

```json

{

"jest": {

"coverageThresholds": {

"global": {

"branches": 80,

"functions": 80,

"lines": 80,

"statements": 80

}

}

}

}

```

❌ 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

})

```

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

```

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

• 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.