import { createNext } from 'e2e-utils' import { NextInstance } from 'e2e-utils' import { check } from 'next-test-utils' describe('useReportWebVitals hook', () => { let next: NextInstance beforeAll(async () => { next = await createNext({ files: __dirname, skipStart: true, env: {}, dependencies: { nanoid: '4.0.1', }, }) await next.start() }) afterAll(() => next.destroy()) // Analytics events are only sent in production it('should send web-vitals', async () => { await next.fetch('/report-web-vitals') let eventsCount = 0 const browser = await next.browser('/report-web-vitals', { beforePageLoad: (page) => { page.route('https://example.vercel.sh/vitals', (route) => { eventsCount += 1 route.fulfill() }) }, }) // Refresh will trigger CLS and LCP. When page loads FCP and TTFB will trigger: await browser.refresh() // After interaction LCP and FID will trigger await browser.elementById('btn').click() // Make sure all registered events in performance-relayer has fired await check(async () => { expect(eventsCount).toBeGreaterThanOrEqual(6) return 'success' }, 'success') }) })