background-image-set-image.html | Explore in Territory

<!DOCTYPE html>
<html>

<head>
  <title>Background image-set images should be LCP candidates</title>
  <script src="/resources/testharness.js"></script>
  <script src="/resources/testharnessreport.js"></script>
  <style>
    .background {
      width: calc(100vw - 40px);
      height: calc(100vw - 40px);
      max-width: 100px;
      max-height: 100px;
      background: #eee image-set('/images/lcp-100x50.png' type('image/png')) center center no-repeat;
      background-size: cover;
    }
  </style>
</head>

<body>
  <div class="background"></div>
  <p>fallback</p>

  <script>
    promise_test(async (t) => {
      t.step_timeout(async () => {
        let lcpEntryNames =
          await new Promise(resolve => {
            new PerformanceObserver((list) => {
              resolve(list.getEntries().map(e => e.url));
            }).observe({ type: "largest-contentful-paint", buffered: true });
          });

        assert_true(lcpEntryNames.find(e => e.includes('lcp-100x50')),
          'Background image-set image should be an LCP candidate.');
      }, 100);
    }, "Background image-set images should be eligible for LCP candidates");
  </script>
</body>

</html>

chromium/third_party/blink/web_tests/external/wpt/largest-contentful-paint/background-image-set-image.html