LayoutTests/intersection-observer/root-element-moved.html

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

<div id="root" style="position:absolute">
    <div id="target" style="width: 100px; height: 100px; background-color: green"></div>
</div>

<script>
    var observer;
    var root = document.getElementById('root');
    var target = document.getElementById('target');
    test(function() {
        observer = new IntersectionObserver(function() {}, { root: document.getElementById('root') });;
        assert_equals(observer.root, root);
        observer.observe(target);
        assert_equals(internals.numberOfIntersectionObservers(document), 1);
        document.body.appendChild(target);
        var newDoc = document.implementation.createHTMLDocument('New document');
        newDoc.body.appendChild(root);
        assert_equals(internals.numberOfIntersectionObservers(document), 0);
        assert_equals(internals.numberOfIntersectionObservers(newDoc), 1);
        document.body.appendChild(root);
        assert_equals(internals.numberOfIntersectionObservers(document), 1);
        assert_equals(internals.numberOfIntersectionObservers(newDoc), 0);
    },"Document's active intersection observers get updated");
</script>
</body>
</html>