LayoutTests/fast/parser/xml-error-unload-iframe.html

<!DOCTYPE html>
<head>
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
</head>
<body>
<script>

let svgElement;
function moveIframe(svgDoc) {
    if (svgElement)
        return;
    svgElement = svgDoc.documentElement;
    const iframe = document.createElement('iframe');
    svgDoc.documentElement.appendChild(iframe);
    iframe.contentWindow.onunload = () => {
        document.body.appendChild(svgElement);
    }
}

const content = `<svg xmlns="http://www.w3.org/2000/svg"><script>parent.moveIframe(document);<\/script><element a="1" a="2"/></svg>`;
const iframe = document.createElement('iframe');
iframe.src = URL.createObjectURL(new Blob([content], {type: 'text/xml'}));
document.documentElement.appendChild(iframe);

window.onload = () => {
    let test = async_test('An element removed by the adoption agency algorithm must not be inserted if it had been inserted elsewhere');
    test.step(() => {
        assert_equals(svgElement.parentNode, document.body);
        svgElement.remove();
    });
    test.done();
}

</script>
</body>