fix flaky test

Author: mydea

dev-packages/browser-integration-tests/suites/tracing/metrics/web-vitals-ttfb/test.ts

@@ -4,15 +4,22 @@ import type { Event } from '@sentry/types';
 import { sentryTest } from '../../../../utils/fixtures';
 import { getFirstSentryEnvelopeRequest, shouldSkipTracingTest } from '../../../../utils/helpers';
 
-sentryTest('should capture TTFB vital.', async ({ getLocalTestPath, page }) => {
+sentryTest('should capture TTFB vital.', async ({ getLocalTestUrl, page }) => {
   if (shouldSkipTracingTest()) {
     sentryTest.skip();
   }
 
-  const url = await getLocalTestPath({ testDir: __dirname });
+  const url = await getLocalTestUrl({ testDir: __dirname });
   const eventData = await getFirstSentryEnvelopeRequest<Event>(page, url);
 
   expect(eventData.measurements).toBeDefined();
-  expect(eventData.measurements?.ttfb?.value).toBeDefined();
+
+  // If responseStart === 0, ttfb is not reported
+  // This seems to happen somewhat randomly, so we just ignore this in that case
+  const responseStart = await page.evaluate("performance.getEntriesByType('navigation')[0].responseStart;");
+  if (responseStart !== 0) {
+    expect(eventData.measurements?.ttfb?.value).toBeDefined();
+  }
+
   expect(eventData.measurements?.['ttfb.requestTime']?.value).toBeDefined();
 });