🦔 posthog-playwright

Playwright matchers for testing PostHog analytics events. Intercepts PostHog network requests and captures events, letting you assert that the right analytics events fire during your E2E tests.

📦 Installation

npm install --save-dev posthog-playwright

🚀 Setup

Extend your Playwright test with PostHog tracking:

// fixtures.ts
import { test as base, expect as baseExpect } from '@playwright/test';
import { withPostHogTracking, matchers } from 'posthog-playwright';

export const test = withPostHogTracking(base);
export const expect = baseExpect.extend(matchers);

Configure PostHog for Testing

PostHog needs specific settings to work reliably in Playwright tests. Add these conditionally in your app:

posthog.init('your-api-key', {
  // Disable bot detection - Playwright is detected as a bot
  opt_out_useragent_filter: process.env.NODE_ENV === 'test',

  // Disable batching in tests - events send immediately
  request_batching: process.env.NODE_ENV !== 'test',
});

Then use in your tests:

// my-test.spec.ts
import { test, expect } from './fixtures';

test('user signup tracking works', async ({ page }) => {
  await page.goto('/signup');
  await page.getByLabel('Email').fill('user@example.com');
  await page.getByText('Sign Up').click();

  // ✅ Assert the event was fired
  await expect(page).toHaveFiredEvent('user_signed_up', {
    plan: 'pro',
    source: 'web'
  });
});

📖 API Reference

withPostHogTracking(test)

Extends a Playwright test instance with PostHog event tracking on the page fixture.

import { test as base } from '@playwright/test';
import { withPostHogTracking } from 'posthog-playwright';

export const test = withPostHogTracking(base);

Works with already-extended tests too:

const testWithAuth = base.extend({
  authenticatedPage: async ({ page }, use) => {
    // ... login logic
    await use(page);
  },
});

export const test = withPostHogTracking(testWithAuth);

matchers

Custom matchers to extend Playwright's expect:

import { expect as baseExpect } from '@playwright/test';
import { matchers } from 'posthog-playwright';

export const expect = baseExpect.extend(matchers);

🎯 Matchers

toHaveFiredEvent(eventName, properties?, config?)

Asserts that a PostHog event was fired. Automatically polls for up to 2 seconds.

// Basic usage
await expect(page).toHaveFiredEvent('button_clicked');

// With property matching (subset match)
await expect(page).toHaveFiredEvent('purchase_completed', {
  plan: 'pro',
  amount: 99.99
});

// With custom timeout
await expect(page).toHaveFiredEvent('slow_event', {}, {
  timeout: 5000,      // Wait up to 5 seconds
  pollInterval: 200   // Check every 200ms
});

💡 Properties Matching: Uses subset matching - the event properties must contain the expected properties but can have additional ones.

notToHaveFiredEvent(eventName, properties?, config?)

Asserts that an event was NOT fired:

await expect(page).notToHaveFiredEvent('error_occurred');

toHaveCapturedEvents(count?)

Asserts that events were captured:

// At least one event
await expect(page).toHaveCapturedEvents();

// Exactly 5 events
await expect(page).toHaveCapturedEvents(5);

🐛 Debug Mode

Enable debug mode via the DEBUG environment variable:

DEBUG=true npx playwright test

🛠️ Utility Functions

import { getCapturedEvents, clearCapturedEvents } from 'posthog-playwright';

test('advanced usage', async ({ page }) => {
  await page.goto('/');

  // Get all captured events
  const events = getCapturedEvents(page);

  // Clear events (useful for multi-step tests)
  clearCapturedEvents(page);
});

📚 Examples

Testing Event Properties

test('tracks user preferences', async ({ page }) => {
  await page.goto('/settings');
  await page.getByLabel('Theme').selectOption('dark');
  await page.getByText('Save').click();

  await expect(page).toHaveFiredEvent('settings_updated', {
    theme: 'dark',
  });
});

Testing a Funnel

test('tracks funnel events', async ({ page }) => {
  await page.goto('/product');
  await expect(page).toHaveFiredEvent('product_viewed');

  await page.getByText('Add to Cart').click();
  await expect(page).toHaveFiredEvent('add_to_cart');

  await page.getByText('Checkout').click();
  await expect(page).toHaveFiredEvent('checkout_started');
});

📄 License

MIT