LayoutTests/media/audio-controls-adoptNode.html

<p>Test that UA shadow from 'controls' attribute is still populated when using adoptNode.<p>
<script src=video-test.js></script>
<script>
var parser = new DOMParser;
mediaElement = parser.parseFromString("<audio controls></audio>", "text/html").body.children[0];

document.body.appendChild(document.adoptNode(mediaElement));

testExpected("mediaElement.getAttribute('controls')", "");

var shadow = window.internals?.shadowRoot(mediaElement);
testExpected("shadow?.childNodes.length", 0, ">");

endTest();

</script>