Imported from jeremylongshore/tons-of-skills-marketplace (skills/.curated/clerk-local-dev-loop/SKILL.md). Install upstream with npx skills add jeremylongshore/tons-of-skills-marketplace --skill clerk-local-dev-loop. Copyright stays with the author (MIT).

Clerk Local Dev Loop

Overview

Configure an efficient local development workflow with Clerk authentication, including test users, hot reload, and mock auth for unit tests.

Prerequisites

• Clerk SDK installed (clerk-install-auth completed)
• Development instance created in Clerk Dashboard
• Node.js development environment

Instructions

Step 1: Configure Development Instance

Create a separate Clerk development instance to isolate test data from production.

# .env.local — use test keys (pk_test_ / sk_test_)
NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY=pk_test_...
CLERK_SECRET_KEY=sk_test_...

# Optional: Enable Clerk debug logging
CLERK_DEBUG=true

Clerk development instances provide:

• No email verification required
• Test phone numbers accepted
• Relaxed rate limits
• OAuth with test credentials

Step 2: Set Up Test Users

// scripts/seed-test-users.ts
import { createClerkClient } from '@clerk/backend'

const clerk = createClerkClient({ secretKey: process.env.CLERK_SECRET_KEY! })

async function seedTestUsers() {
  const users = [
    { emailAddress: ['admin@test.com'], password: 'test1234', firstName: 'Admin', lastName: 'User' },
    { emailAddress: ['member@test.com'], password: 'test1234', firstName: 'Member', lastName: 'User' },
  ]

  for (const user of users) {
    try {
      await clerk.users.createUser(user)
      console.log(`Created: ${user.emailAddress[0]}`)
    } catch (err: any) {
      if (err.status === 422) {
        console.log(`Already exists: ${user.emailAddress[0]}`)
      } else {
        throw err
      }
    }
  }
}

seedTestUsers()

Run with:

npx tsx scripts/seed-test-users.ts

Step 3: Configure Hot Reload

// next.config.ts — ensure Clerk works with hot reload
const nextConfig = {
  // Clerk SDK is compatible with Turbopack
  experimental: {
    // turbo: {}, // Uncomment if using Turbopack
  },
  // Prevent Clerk SDK from being bundled incorrectly
  serverExternalPackages: ['@clerk/backend'],
}

export default nextConfig

# Start dev server with HTTPS (required for some Clerk features)
npx next dev --experimental-https

Step 4: Development Scripts

// package.json scripts
{
  "scripts": {
    "dev": "next dev",
    "dev:https": "next dev --experimental-https",
    "dev:seed": "tsx scripts/seed-test-users.ts",
    "dev:tunnel": "ngrok http 3000",
    "dev:webhook": "ngrok http 3000 --log stdout"
  }
}

Step 5: Mock Authentication for Tests

// test/helpers/clerk-mock.ts
import { vi } from 'vitest'

export function mockClerkAuth(overrides: { userId?: string; orgId?: string } = {}) {
  const mockAuth = {
    userId: overrides.userId || 'user_test_123',
    orgId: overrides.orgId || null,
    getToken: vi.fn().mockResolvedValue('mock_token'),
    has: vi.fn().mockReturnValue(true),
  }

  vi.mock('@clerk/nextjs/server', () => ({
    auth: vi.fn().mockResolvedValue(mockAuth),
    currentUser: vi.fn().mockResolvedValue({
      id: mockAuth.userId,
      firstName: 'Test',
      lastName: 'User',
      emailAddresses: [{ emailAddress: 'test@test.com' }],
    }),
    clerkMiddleware: vi.fn(() => (req: any, res: any, next: any) => next()),
  }))

  return mockAuth
}

// test/api/data.test.ts
import { describe, it, expect, beforeEach } from 'vitest'
import { mockClerkAuth } from '../helpers/clerk-mock'

describe('GET /api/data', () => {
  beforeEach(() => {
    mockClerkAuth({ userId: 'user_test_123' })
  })

  it('returns data for authenticated user', async () => {
    const res = await fetch('/api/data')
    expect(res.status).toBe(200)
  })
})

Output

• Development instance with test keys configured
• Test users seeded via script
• HTTPS dev server running for Clerk compatibility
• Vitest mock helpers for auth in unit tests

Error Handling

Examples

Playwright Auth Fixture for E2E Tests

// e2e/fixtures/auth.ts
import { test as base } from '@playwright/test'

export const test = base.extend({
  authenticatedPage: async ({ page }, use) => {
    await page.goto('/sign-in')
    await page.fill('input[name="identifier"]', 'admin@test.com')
    await page.click('button:has-text("Continue")')
    await page.fill('input[name="password"]', 'test1234')
    await page.click('button:has-text("Continue")')
    await page.waitForURL('/dashboard')
    await use(page)
  },
})

Resources

• Clerk Development Mode
• Clerk Testing Guide
• Next.js HTTPS Dev

Next Steps

Proceed to clerk-sdk-patterns for common SDK usage patterns.