posthog-local-dev-loop

# PostHog Local Dev Loop ## Overview Set up a fast local development workflow for PostHog integrations. Covers debug mode for event inspection, mocking posthog-node for unit tests, and a dev/test PostHog project to avoid polluting production data. ## Prerequisites - Completed `posthog-install-auth` setup - Node.js 20+ with npm/pnpm - Vitest or Jest for testing - Separate PostHog project for development (recommended) ## Instructions ### Step 1: Project Structure ``` my-posthog-app/ ├── src/ │ ├── analytics/ │ │ ├── posthog.ts # Singleton client │ │ ├── events.ts # Event taxonomy (typed constants) │ │ └── flags.ts # Feature flag keys │ └── index.ts ├── tests/ │ ├── analytics.test.ts # Unit tests with mocked PostHog │ └── integration.test.ts # Integration tests (real PostHog dev project) ├── .env.local # Dev keys (git-ignored) ├── .env.example # Template: NEXT_PUBLIC_POSTHOG_KEY=phc_... └── package.json ``` ### Step 2: PostHog Client with Dev Mode ```typescript // src/analytics/posthog.ts import { PostHog } from 'posthog-node'; let client: PostHog | null = null; export function getPostHog(): PostHog { if (!client) { client = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, { host: process.env.POSTHOG_HOST || 'https://us.i.posthog.com', flushAt: process.env.NODE_ENV === 'development' ? 1 : 20, flushInterval: process.env.NODE_ENV === 'development' ? 0 : 10000, ...