tdd-workflow skill

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 (Playwright)

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

TDD Workflow Steps

Step 0: Detect the Test Runner

Do not assume npm test. The commands in the steps and examples below use , , and as placeholders for the project's actual runner. Resolve them once before starting:

1. Run the package-manager detector (ships with ECC):

node scripts/setup-package-manager.js --detect

It resolves the package manager (npm / pnpm / yarn / bun) from, in order: CLAUDEPACKAGEMANAGER, .claude/package-manager.json, the package.json packageManager field, the lockfile, then global config.

1. Distinguish the package manager from the test runner — they are not the same. A project can use Bun to install dependencies yet still run Jest or Vitest. Inspect package.json scripts.test and the test files:

• scripts.test invokes jest / vitest -> run through the detected PM (npm test, pnpm test, yarn test, or bun run test).
• scripts.test is bun test, or test files import { test, expect } from "bun:test", or there is no jest/vitest config but Bun is present -> use Bun's native runner (bun test). See Bun Native Test Pattern below.

Runner command matrix:

bun test (Bun's built-in runner) is not the same as bun run test (which runs the package.json test script). Picking the wrong one is a common failure — e.g. invoking Jest through npx/bun run in an ESM-only project breaks, while bun test runs the suite natively. Confirm which the project expects before the RED gate, then substitute / everywhere npm test appears below.

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:

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)

<test>
# Tests should fail - we haven't implemented yet

Step 4: Implement Code

Write minimal code to make tests pass:

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

Step 5: Run Tests Again

<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

<coverage>
# Verify 80%+ coverage achieved

Testing Patterns

Unit Test Pattern (Jest/Vitest)

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()
  })
})

Bun Native Test Pattern (bun:test)

When the project uses Bun's built-in runner (see Step 0), import from bun:test and run with bun test — not bun run test. The API is Jest-like, so describe / it / expect and most matchers carry over. See the bun-runtime skill for runtime, install, and bundler details.

import { describe, it, expect, mock } from 'bun:test'
import { searchMarkets } from './search'

describe('searchMarkets', () => {
  it('returns an empty list for an empty query', async () => {
    expect(await searchMarkets('')).toEqual([])
  })

  it('sorts results by similarity score', async () => {
    const results = await searchMarkets('election')
    expect(results).toEqual([...results].sort((a, b) => b.score - a.score))
  })
})

bun test              # run once (RED/GREEN gate)
bun test --watch      # watch mode during development
bun test --coverage   # coverage report

• Mock modules with mock.module(...) / mock(...) from bun:test instead of jest.mock(...).
• Configure coverage thresholds in bunfig.toml under [test] (e.g. coverageThreshold) rather than the Jest coverageThresholds config block.

API Integration Test Pattern

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)

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.f

Test File Organization

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

Mocking External Services

Supabase Mock

jest.mock('@/lib/supabase', () => ({
  supabase: {
    from: jest.fn(() => ({
      select: jest.fn(() => ({
        eq: jest.fn(() => Promise.resolve({
          data: [{ id: 1, name: 'Test Market' }],
          error: null
        }))
      }))
    }))
  }
}))