shadow-dom/assign-slottables-after-removing-shadow-tree-from-document.html

<!DOCTYPE html>
<head>
    <title>Slottables should match slots when the shadow host is removed from the document</title>
    <meta name="author" title="Simon Wülker" href="mailto:simon.wuelker@arcor.de">
    <meta name="assert" content="Slottables should be assigned to slots even after the shadow host has been removed from the document">
    <link rel="help" href="https://github.com/servo/servo/issues/40242">

    <script src="/resources/testharness.js"></script>
    <script src="/resources/testharnessreport.js"></script>
</head>

<body>
    <script defer>
      test((t) => {
        // Attach a shadow root with a slot named "foo" inside it
        let host = document.createElement("div");
        document.body.appendChild(host);
        let root = host.attachShadow({mode: "closed"});
        let slot = document.createElement("slot");
        slot.name = "foo";
        root.appendChild(slot);

        // Remove the host from the document tree
        host.remove();
        assert_array_equals(slot.assignedNodes(), []);

        // Create a slottable that should be slotted into "foo"
        let slottable = document.createElement("div");
        slottable.slot = "foo"
        host.appendChild(slottable);
        assert_array_equals(slot.assignedNodes(), [slottable]);
      }, "Slottables should be assigned to slots even after the shadow host has been removed from the document");
    </script>
</body>