chromium/src/third_party/blink/web_tests/external/wpt/html/semantics/embedded-content/the-iframe-element/iframe-first-load-canceled-second-load-blank.html

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

// Check about:blank navigation is asynchronous, even if the initial navigation
// is canceled.
promise_test(async test => {
  // Wait for document.body to exist, before appending the <iframe>.
  await new Promise(resolve => window.onload = resolve);

  // The initial navigation in this new iframe will result in a 204 No Content.
  // As a result the navigation will be canceled. The <iframe> will stay on the
  // initial empty document.
  const iframe = document.createElement("iframe");
  iframe.src = "/common/blank.html?pipe=status(204)"
  document.body.appendChild(iframe);

  // The navigation in the iframe will be canceled. There are no good ways to
  // detect when it will happen. Anyway, any additional navigation must be
  // asynchronous. To test what happens when there are no pending navigation,
  // waiting one second should be enough, most of the time.
  await new Promise(resolve => test.step_timeout(resolve, 1000));

  let load_event_fired = false;
  const load_event_promise = new Promise(resolve => {
    iframe.onload = () => {
      load_event_fired = true;
      resolve();
    };
  });
  iframe.src = "about:blank";
  assert_equals(load_event_fired, false,
    "about:blank must not commit synchronously");
  await load_event_promise;
}, "about:blank navigation is asynchronous, even if the initial one is " +
  "canceled.");

</script>