update-on-style-change.html | Explore in Territory

<!DOCTYPE html>
<meta charset="utf-8">
<title>LargestContentfulPaint entries should NOT be emitted for updates to previous LargestContentfulPaint elements.</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<body>
  <script>
      promise_test(async (t) => {
      assert_implements(window.LargestContentfulPaint, "LargestContentfulPaint is not implemented");
      let lcpEntries = [];
      await new Promise(resolve => t.step_timeout(() => {
        new PerformanceObserver(list => {
          lcpEntries = lcpEntries.concat(list.getEntries())
          if (lcpEntries.length > 1) {
            assert_unreached("There shouldn't be more than 1 LCP entry for an element.");
          }
          if (lcpEntries) {
            assert_equals(lcpEntries.length, 1, "There should be only 1 LCP entry for one element. ");
            assert_equals(lcpEntries[0].id, "text", "The LCP should have id 'text'");
            resolve();
          }
        }).observe({ type: 'largest-contentful-paint', buffered: true });
      }, 200));
    })
  </script>
  <div id="text">text</div>
  <link rel="stylesheet" href="/resources/slow-style-change.py">
</body>

chromium/third_party/blink/web_tests/external/wpt/largest-contentful-paint/update-on-style-change.html