fullscreen/api/element-request-fullscreen-same.html

<!DOCTYPE html>
<title>Element#requestFullscreen() on the current fullscreen element</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>
<div id="log"></div>
<div id="target"></div>
<script>
    promise_test(async (t) => {
        const target = document.getElementById("target");
        document.onfullscreenerror = t.unreached_func("fullscreenerror event");

        await Promise.all([
            fullScreenChange(),
            trusted_request(target),
        ]);

        assert_equals(document.fullscreenElement, target);

        // The next requestFullscreen() should fire no events due to "If element is
        // doc's fullscreen element, terminate these subsubsteps."
        document.onfullscreenchange = t.unreached_func(
            "fullscreenchange event"
        );

        await trusted_click(target);
        await target.requestFullscreen();
        assert_equals(document.fullscreenElement, target);
        // Wait until after the next animation frame.
        await new Promise((r) => requestAnimationFrame(r));
    }, "Element#requestFullscreen() on the current fullscreen element");
</script>