web-platform-tests
diff --git a/‎shadow-dom/declarative/clonable.window.js
-10 b/‎shadow-dom/declarative/clonable.window.js
-10
diff --git a/‎shadow-dom/shadow-root-clonable.html
+49 b/‎shadow-dom/shadow-root-clonable.html
+49
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<title>Shadow root clonable flag</title>
+<link rel='author' href='mailto:[email protected]'>
+<link rel='author' href='mailto:[email protected]'>
+<link rel='help' href='https://dom.spec.whatwg.org/#shadowroot-clonable'>
+<script src='/resources/testharness.js'></script>
+<script src='/resources/testharnessreport.js'></script>
+
+<body>
+<script>
+test(() => {
+  const div = document.createElement("div");
+  const root = div.attachShadow({ mode: "open", clonable: true });
+  root.appendChild(document.createElement("input"));
+  assert_true(root.clonable, "clonable attribute");
+
+  const clone = div.cloneNode(true);
+  const clonedRoot = clone.shadowRoot;
+  assert_true(clonedRoot.clonable, "clone gets the same clonable state");
+  assert_equals(clonedRoot.children.length, 1, "children count");
+  assert_equals(clonedRoot.children[0].localName, "input", "children content");
+}, "attachShadow with clonable: true");
+
+for (const clonable of [false, undefined]) {
+  test(() => {
+    const div = document.createElement("div");
+    const root = div.attachShadow({ mode: "open", clonable });
+    root.appendChild(document.createElement("input"));
+    assert_false(root.clonable, "clonable attribute");
+
+    const clone = div.cloneNode(true);
+    assert_true(!clone.shadowRoot, "shadow should not be cloned");
+  }, `attachShadow with clonable: ${clonable}`);
+}
+
+test(() => {
+  const div = document.createElement("div");
+  div.setHTMLUnsafe('<div><template shadowrootmode=open><input></template></div>');
+  const root = div.firstElementChild.shadowRoot;
+  assert_true(!!root);
+  assert_true(root.clonable, "clonable is automatically true for declarative shadow root");
+
+  const clone = div.cloneNode(true);
+  const clonedRoot = clone.firstElementChild.shadowRoot;
+  assert_true(!!clonedRoot);
+  assert_equals(clonedRoot.children.length, 1, "children count");
+  assert_equals(clonedRoot.children[0].localName, "input", "children content");
+}, "declarative shadow roots get clonable: true automatically");
+</script>