chromium/content/test/data/accessibility/html/popover-collapsed.html

<!--
@BLINK-ALLOW:expanded*
@WAIT-FOR:PopoverNowClosed
-->

<!DOCTYPE html>

<button id=toggle popovertarget="will-collapse">Will collapse</button>
<div popover id="will-collapse">PopoverVisible</div>

<script>
// This test could be written in the trivial way: with the HTML above, but
// never showing or hiding the popover. Instead, it opens the popover, waits
// for the a11y tree to get sync'd, and then closes the popover and waits again,
// to make sure those updates are captured.

document.addEventListener('DOMContentLoaded', () => {
  const a11ySyncTimeMs = 500;
  const popover = document.getElementById('will-collapse');
  popover.showPopover(); // Start expanded.
  const button = document.getElementById('toggle');
  setTimeout(() => {
    requestAnimationFrame(() => {
      requestAnimationFrame(() => {
        // A11y tree should be up to date now, with the popover visible.
        button.click();
        setTimeout(() => {
          requestAnimationFrame(() => {
            requestAnimationFrame(() => {
              // Signal the end of the test.
              document.title = 'PopoverNowClosed';
            });
          });
        },a11ySyncTimeMs);
      });
    });
  },a11ySyncTimeMs);
});
</script>