stale-image.html - mozsearch

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This test has a WPT meta file that expects 1 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /fetch/stale-while-revalidate/stale-image.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<meta charset="utf-8">

<title>Tests Stale While Revalidate works for images</title>

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<script src="/common/utils.js"></script>

<body>

<!--

Use a child document to load the second stale image into because

an image loaded into the same document will skip cache-control headers.

See: https://html.spec.whatwg.org/#the-list-of-available-images

-->

<iframe id="child1" srcdoc=""></iframe>

<iframe id="child2" srcdoc=""></iframe>

<script>

var request_token = token();

let image_src = "resources/stale-image.py?token=" + request_token;

let loadImage = async (document) => {

  let img = document.createElement("img");

  img.src = image_src;

  let loaded = new Promise(r => img.onload = r);

  document.body.appendChild(img);

  await loaded;

  return img;

};

promise_test(async t => {

  await new Promise(r => window.onload = r);

  let img1 = await loadImage(document);

  assert_equals(img1.width, 16, "(initial version loaded)");

  let img2 = await loadImage(child1.contentDocument);

  assert_equals(img2.width, 16, "(stale version loaded)");

  // Query the server again and again. At some point it must have received the

  // revalidation request. We poll, because we don't know when the revalidation

  // will occur.

  while(true) {

    await new Promise(r => step_timeout(r, 25));

    let response = await fetch(image_src + "&query");

    let count = response.headers.get("Count");

    if (count == '2')

      break;

  let img3 = await loadImage(child2.contentDocument);

  assert_equals(img3.width, 256, "(revalidated version loaded)");

}, 'Cache returns stale resource');

</script>

</body>