image-loading-lazy-move-document.html

<!DOCTYPE html>
<head>
<title>Moving loading='lazy' image into another top level document</title>
<link rel="help" href="https://github.com/scott-little/lazyload">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
</head>

<div style="height:1000vh;"></div>
<img loading="lazy"
     src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAIAAAAC64paAAAAG0lEQVR42mP8z0A%2BYKJA76jmUc2jmkc1U0EzACKcASfOgGoMAAAAAElFTkSuQmCC">
<script>
promise_test(async t => {
  let image_loaded = false;
  const img = document.querySelector("img");
  img.addEventListener("load", () => { image_loaded = true; });

  await new Promise(resolve => window.addEventListener("load", resolve));

  assert_false(image_loaded,
               "lazy-load image shouldn't be loaded yet");

  const anotherWin = window.open("resources/newwindow.html");

  await new Promise(resolve => anotherWin.addEventListener("load", resolve));

  anotherWin.document.body.appendChild(img);

  assert_false(image_loaded,
               "lazy-load image shouldn't be loaded yet");

  img.scrollIntoView();

  await new Promise(resolve => img.addEventListener("load", resolve));
  assert_true(img.complete,
              "Now the lazy-load image should be loaded");
});
</script>

chromium/third_party/blink/web_tests/external/wpt/html/semantics/embedded-content/the-img-element/image-loading-lazy-move-document.html