fullscreen/api/element-request-fullscreen-two-elements.html

<!DOCTYPE html>
<title>Element#requestFullscreen() on two elements in the same document</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-vendor.js"></script>
<script src="../trusted-click.js"></script>
<body>
    <div id="a"></div>
    <div id="b"></div>
</body>
<script>
    promise_test(async (t) => {
        document.onfullscreenerror = t.unreached_func("fullscreenerror event");

        // Request fullscreen on both elements, but in reverse tree order.
        const a = document.getElementById("a");
        const b = document.getElementById("b");

        // Expect two fullscreenchange events, with document.fullscreenElement
        // changing in the same order as the requests.
        await trusted_click(b);
        await Promise.all([b.requestFullscreen(), fullScreenChange()]);
        assert_equals(document.fullscreenElement, b);

        await trusted_click(b);
        await Promise.all([a.requestFullscreen(), fullScreenChange()]);
        assert_equals(document.fullscreenElement, a);
    }, "Element#requestFullscreen() on two elements in the same document");
</script>