---

name: posthog-local-dev-loop description: | Configure PostHog local development with hot reload and testing. Use when setting up a development environment, configuring test workflows, or establishing a fast iteration cycle with PostHog. Trigger with phrases like "posthog dev setup", "posthog local development", "posthog dev environment", "develop with posthog". allowed-tools: Read, Write, Edit, Bash(npm:), Bash(pnpm:), Grep version: 1.0.0 license: MIT author: Jeremy Longshore jeremy@intentsolutions.io

PostHog Local Dev Loop

Overview

Set up a fast, reproducible local development workflow for PostHog.

Prerequisites

• Completed posthog-install-auth setup
• Node.js 18+ with npm/pnpm
• Code editor with TypeScript support
• Git for version control

Instructions

Step 1: Create Project Structure

my-posthog-project/
├── src/
│   ├── posthog/
│   │   ├── client.ts       # PostHog client wrapper
│   │   ├── config.ts       # Configuration management
│   │   └── utils.ts        # Helper functions
│   └── index.ts
├── tests/
│   └── posthog.test.ts
├── .env.local              # Local secrets (git-ignored)
├── .env.example            # Template for team
└── package.json

Step 2: Configure Environment

# Copy environment template
cp .env.example .env.local

# Install dependencies
npm install

# Start development server
npm run dev

Step 3: Setup Hot Reload

{
  "scripts": {
    "dev": "tsx watch src/index.ts",
    "test": "vitest",
    "test:watch": "vitest --watch"
  }
}

Step 4: Configure Testing

import { describe, it, expect, vi } from 'vitest';
import { PostHogClient } from '../src/posthog/client';

describe('PostHog Client', () => {
  it('should initialize with API key', () => {
    const client = new PostHogClient({ apiKey: 'test-key' });
    expect(client).toBeDefined();
  });
});

Output

• Working development environment with hot reload
• Configured test suite with mocking
• Environment variable management
• Fast iteration cycle for PostHog development

Error Handling

Error	Cause	Solution
Module not found	Missing dependency	Run npm install
Port in use	Another process	Kill process or change port
Env not loaded	Missing .env.local	Copy from .env.example
Test timeout	Slow network	Increase test timeout

Examples

Mock PostHog Responses

vi.mock('@posthog/sdk', () => ({
  PostHogClient: vi.fn().mockImplementation(() => ({
    // Mock methods here
  })),
}));

Debug Mode

# Enable verbose logging
DEBUG=POSTHOG=* npm run dev

Resources

• PostHog SDK Reference
• Vitest Documentation
• tsx Documentation

Next Steps

See posthog-sdk-patterns for production-ready code patterns.