<!DOCTYPE html>
<html>
<head>
<style>
dialog {
    height: 150px;
    width: 150px;
}

::backdrop {
    display: none;
}

.red {
    background-color: red;
    top: 200px;
}

#bottomDialog {
    background-color: blue;
    top: 50px;
}

#topDialog {
    background-color: green;
    top: 100px;
    left: 50px;
}
</style>
</head>
<body>
This tests top layer element stacking order after dynamically calling show/close and removal from the DOM tree.
The test passes if you see a green rectangle stacked on top of a blue rectangle, and see no red rectangles.

<dialog id="topDialog"></dialog>
<dialog id="bottomDialog"></dialog>
<dialog id="removedDialog" class="red">
    <dialog id="removedDialogChild" class="red"></dialog>
</dialog>
<script>
document.getElementById('topDialog').showModal();
var removedDialog = document.getElementById('removedDialog');
removedDialog.showModal();
document.getElementById('bottomDialog').showModal();
document.getElementById('removedDialogChild').showModal();
removedDialog.parentNode.removeChild(removedDialog);
document.getElementById('topDialog').close();
document.getElementById('topDialog').showModal();
</script>
</body>
</html>