1 files changed, 34 insertions, 0 deletions
diff --git a/testing/web-platform/tests/dom/nodes/insertion-removing-steps/Node-appendChild-script-and-custom-from-fragment.tentative.html b/testing/web-platform/tests/dom/nodes/insertion-removing-steps/Node-appendChild-script-and-custom-from-fragment.tentative.html
new file mode 100644
index 0000000000..23a050f37e
--- /dev/null
+++ b/testing/web-platform/tests/dom/nodes/insertion-removing-steps/Node-appendChild-script-and-custom-from-fragment.tentative.html
@@ -0,0 +1,34 @@
+<!doctype html>
+<meta charset=utf-8>
+<title>Node.appendChild: inserting script and custom element from a DocumentFragment</title>
+<script src=/resources/testharness.js></script>
+<script src=/resources/testharnessreport.js></script>
+<body>
+<script>
+let customConstructed = false;
+let customConstructedDuringEarlierScript = false;
+class CustomElement extends HTMLElement {
+    constructor() {
+        super();
+        customConstructed = true;
+    }
+}
+test(() => {
+  const script = document.createElement("script");
+  script.textContent = `
+    customElements.define("custom-element", CustomElement);
+    customConstructedDuringEarlierScript = customConstructed;
+  `;
+  const custom = document.createElement("custom-element");
+  const df = document.createDocumentFragment();
+  df.appendChild(script);
+  df.appendChild(custom);
+  assert_false(customConstructed);
+  assert_false(customConstructedDuringEarlierScript);
+  document.head.appendChild(df);
+  assert_true(customConstructed);
+  assert_true(customConstructedDuringEarlierScript);
+}, "An earlier-inserted script can upgrade a later-inserted custom element, " +
+   "whose upgrading is synchronously observable to the script, since DOM " +
+   "insertion has been completed by the time it runs");
+</script>