PostHog CI Integration Skill

PostHog CI Integration

Overview

Set up CI/CD pipelines for PostHog integrations. Covers mocked unit tests (no API key needed), integration tests against a PostHog dev project, and deployment annotations that mark releases in your PostHog timeline.

Prerequisites

GitHub repository with Actions enabled
PostHog dev project API key for integration tests
PostHog personal API key for deployment annotations
npm/pnpm project with vitest or jest

Instructions

Step 1: Configure GitHub Secrets

set -euo pipefail
# Project key for integration tests (phc_... from dev project)
gh secret set POSTHOG_TEST_KEY --body "phc_dev_project_key"

# Personal key for deployment annotations (phx_...)
gh secret set POSTHOG_PERSONAL_API_KEY --body "phx_your_personal_key"

# Project ID for annotations
gh secret set POSTHOG_PROJECT_ID --body "12345"

Step 2: GitHub Actions Workflow

# .github/workflows/posthog-tests.yml
name: PostHog Tests

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  unit-tests:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'
      - run: npm ci
      - run: npm test -- --coverage
        # Unit tests use mocked PostHog — no API key needed

  integration-tests:
    runs-on: ubuntu-latest
    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
    needs: unit-tests
    env:
      NEXT_PUBLIC_POSTHOG_KEY: ${{ secrets.POSTHOG_TEST_KEY }}
      POSTHOG_HOST: https://us.i.posthog.com
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'
      - run: npm ci
      - run: npm run test:integration
        timeout-minutes: 5

  annotate-deploy:
    runs-on: ubuntu-latest
    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
    needs: integration-tests
    steps:
      - name: Create PostHog annotation
        env:
          POSTHOG_PERSONAL_API_KEY: ${{ secrets.POSTHOG_PERSONAL_API_KEY }}
          POSTHOG_PROJECT_ID: ${{ secrets.POSTHOG_PROJECT_ID }}
        run: |
          curl -X POST "https://app.posthog.com/api/projects/$POSTHOG_PROJECT_ID/annotations/" \
            -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" \
            -H "Content-Type: application/json" \
            -d "{
              \"content\": \"Deploy: ${GITHUB_SHA::8} — ${GITHUB_EVENT_HEAD_COMMIT_MESSAGE:-$(git log -1 --pretty=%s)}\",
              \"date_marker\": \"$(date -u +%Y-%m-%dT%H:%M:%SZ)\",
              \"scope\": \"project\"
            }"

Step 3: Unit Tests with Mocked PostHog

// tests/analytics.test.ts — runs in CI without any API keys
import { describe, it, expect, vi, beforeEach } from 'vitest';

vi.mock('posthog-node', () => ({
  PostHog: vi.fn().mockImplementation(() => ({
    capture: vi.fn(),
    identify: vi.fn(),
    getFeatureFlag: vi.fn().mockResolvedValue('control'),
    isFeatureEnabled: vi.fn().mockResolvedValue(true),
    getAllFlags: vi.fn().mockResolvedValue({ 'new-feature': true }),
    flush: vi.fn().mockResolvedValue(undefined),
    shutdown: vi.fn().mockResolvedValue(undefined),
  })),
}));

import { PostHog } from 'posthog-node';

describe('PostHog Analytics', () => {
  let ph: InstanceType<typeof PostHog>;

  beforeEach(() => {
    vi.clearAllMocks();
    ph = new PostHog('phc_test');
  });

  it('captures events with required properties', () => {
    ph.capture({
      distinctId: 'user-1',
      event: 'subscription_started',
      properties: { plan: 'pro', interval: 'annual' },
    });

    expect(ph.capture).toHaveBeenCalledWith(
      expect.objectContaining({
        event: 'subscription_started',
        properties: expect.objectContaining({ plan: 'pro' }),
      })
    );
  });

  it('evaluates feature flags with default fallback', async () => {
    const enabled = await ph.isFeatureEnabled('new-feature', 'user-1');
    expect(enabled).toBe(true);
  });

  it('gets multivariate flag variant', async () => {
    const variant = await ph.getFeatureFlag('experiment', 'user-1');
    expect(variant).toBe('control');
  });
});

Step 4: Integration Tests (Real PostHog Project)

// tests/integration/posthog.test.ts
import { describe, it, expect, afterAll } from 'vitest';
import { PostHog } from 'posthog-node';

const KEY = process.env.NEXT_PUBLIC_POSTHOG_KEY;

describe.skipIf(!KEY)('PostHog Integration', () => {
  const ph = new PostHog(KEY!, {
    host: process.env.POSTHOG_HOST || 'https://us.i.posthog.com',
    flushAt: 1,
    flushInterval: 0,
  });

  afterAll(async () => await ph.shutdown());

  it('captures and flushes an event', async () => {
    ph.capture({
      distinctId: `ci-${Date.now()}`,
      event: 'ci_integration_test',
      properties: {
        ci: true,
        run_id: process.env.GITHUB_RUN_ID || 'local',
      },
    });
    await expect(ph.flush()).resolves.not.toThrow();
  });

  it('evaluates feature flags', async () => {
    const flags = await ph.getAllFlags(`ci-${Date.now()}`);
    expect(typeof flags).toBe('object');
  });

  it('resolves decide endpoint', async () => {
    const response = await fetch('https://us.i.posthog.com/decide/?v=3', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ api_key: KEY, distinct_id: 'ci-test' }),
    });
    expect(response.status).toBe(200);
    const data = await response.json();
    expect(data).toHaveProperty('featureFlags');
  });
});

Step 5: Package Scripts

{
  "scripts": {
    "test": "vitest run",
    "test:integration": "vitest run tests/integration/",
    "test:coverage": "vitest run --coverage"
  }
}

Error Handling

| Issue | Cause | Solution | |-------|-------|----------| | Integration tests fail in CI | Secret not configured | Run gh secret set POSTHOG_TEST_KEY | | Tests timeout | PostHog unreachable from CI runner | Increase timeout, add retry | | Annotation fails | Wrong personal key | Verify phx_ key, check project ID | | Mock type mismatch | PostHog SDK updated | Update mock to match new SDK exports |

Output

Unit test suite with mocked PostHog (runs everywhere, no keys needed)
Integration test suite against PostHog dev project (runs on main only)
Deployment annotations marking each release in PostHog timeline
GitHub Actions workflow with proper secret management

Resources

Next Steps

For deployment patterns, see posthog-deploy-integration.

Agent Skills: PostHog CI Integration

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Skill Files