1 files changed, 32 insertions, 0 deletions
diff --git a/testing/web-platform/tests/custom-elements/upgrading/Document-importNode-customized-builtins.html b/testing/web-platform/tests/custom-elements/upgrading/Document-importNode-customized-builtins.html
new file mode 100644
index 0000000000..91c9ea8aee
--- /dev/null
+++ b/testing/web-platform/tests/custom-elements/upgrading/Document-importNode-customized-builtins.html
@@ -0,0 +1,32 @@
+<!DOCTYPE html>
+<link rel="help" href="https://dom.spec.whatwg.org/#dom-document-importnode">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/custom-elements-helpers.js"></script>
+<body>
+<script>
+test_with_window((w, doc) => {
+  class MyDiv extends HTMLDivElement {}
+  class MyDiv2 extends w.HTMLDivElement {}
+  customElements.define('my-div', MyDiv, { extends: 'div' });
+  w.customElements.define('my-div', MyDiv2, { extends: 'div' });
+
+  let original = document.createElement('div', { is: 'my-div' });
+  assert_true(original instanceof MyDiv);
+
+  let imported = doc.importNode(original);
+  assert_true(imported instanceof MyDiv2);
+}, 'built-in: document.importNode() should import custom elements successfully');
+
+test_with_window((w, doc) => {
+  class MyDiv2 extends w.HTMLDivElement {}
+  w.customElements.define('my-div2', MyDiv2, { extends: 'div' });
+
+  let original = document.createElement('div', { is: 'my-div2' });
+  assert_equals(original.constructor, HTMLDivElement);
+
+  let imported = doc.importNode(original);
+  assert_true(imported instanceof MyDiv2);
+}, 'built-in: document.importNode() should import "undefined" custom elements successfully');
+</script>
+</body>