1 files changed, 64 insertions, 0 deletions
diff --git a/testing/web-platform/tests/dom/nodes/moveBefore/tentative/css-transition-cross-shadow.html b/testing/web-platform/tests/dom/nodes/moveBefore/tentative/css-transition-cross-shadow.html
new file mode 100644
index 0000000000..145f40ba50
--- /dev/null
+++ b/testing/web-platform/tests/dom/nodes/moveBefore/tentative/css-transition-cross-shadow.html
@@ -0,0 +1,64 @@
+<!DOCTYPE html>
+<title>Node.moveBefore should not preserve CSS transition state when crossing shadow boundaries</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+
+<body>
+  <section id="old-parent">
+    <div id="item"></div>
+  </section>
+  <div id="shadow-container">
+    <template shadowrootmode="open">
+      <style>
+        #item {
+          width: 100px;
+          height: 100px;
+          background: green;
+          transition: left 10s;
+          position: absolute;
+          left: 0;
+        }
+
+        section {
+          position: relative;
+        }
+
+        body {
+          margin-left: 0;
+        }
+      </style>
+      <section id="new-parent">
+      </section>
+    </template>
+  </div>
+  <style>
+    #item {
+      width: 100px;
+      height: 100px;
+      background: green;
+      transition: left 10s;
+      position: absolute;
+      left: 0;
+    }
+
+    section {
+      position: relative;
+    }
+
+    body {
+      margin-left: 0;
+    }
+  </style>
+  <script>
+    promise_test(async t => {
+      const item = document.querySelector("#item");
+      assert_equals(item.getBoundingClientRect().x, 0);
+      item.style.left = "400px";
+      await new Promise(resolve => item.addEventListener("transitionstart", resolve));
+      const shadowContainer = document.querySelector("#shadow-container");
+      shadowContainer.shadowRoot.querySelector("#new-parent").moveBefore(item, null);
+      await new Promise(resolve => requestAnimationFrame(() => resolve()));
+      assert_greater_than(item.getBoundingClientRect().x, 399);
+    }, "Moving an element with a transition across shadow boundaries should reset the transition");
+  </script>
+</body>