<!DOCTYPE html>
<html>
<body>
<script>
onload = () => {
    setTimeout(() => {
        window.prompt("PASS: This prompt dialog should show");
        window.confirm("PASS: This confirm dialog should show");
        window.alert("PASS: This alert dialog should show");
        top.postMessage("done", "*");
    }, 0);
};
</script>
</body>
</html>