1 files changed, 50 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/dom/elements/global-attributes/the-anchor-attribute-002.tentative.html b/testing/web-platform/tests/html/dom/elements/global-attributes/the-anchor-attribute-002.tentative.html
new file mode 100644
index 0000000000..a1a237a2ee
--- /dev/null
+++ b/testing/web-platform/tests/html/dom/elements/global-attributes/the-anchor-attribute-002.tentative.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<link rel="help" href="https://github.com/whatwg/html/pull/9144">
+<link rel="author" href="mailto:xiaochengh@chromium.org">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+
+<style>
+body {
+  margin: 0;
+}
+.anchor {
+  width: 100px;
+  height: 100px;
+  margin-left: 50px;
+  margin-top: 50px;
+  background: orange;
+}
+.target {
+  position: absolute;
+  left: anchor(right, 123px);
+  top: anchor(top, 456px);
+  width: 100px;
+  height: 100px;
+  background: lime;
+}
+</style>
+<div class="anchor" id="anchor1"></div>
+<div class="anchor" id="anchor2"></div>
+<div class="target" id="target1" anchor="anchor1"></div>
+<div class="target" id="target2" anchor="anchor1"></div>
+
+<script>
+test(() => {
+  document.body.offsetLeft; // Force layout
+  target1.setAttribute('anchor', 'anchor2');
+  assert_equals(target1.offsetLeft, 150);
+  assert_equals(target1.offsetTop, 200);
+
+  target1.setAttribute('anchor', 'anchor1');
+  assert_equals(target1.offsetLeft, 150);
+  assert_equals(target1.offsetTop, 50);
+}, 'Layout should be updated when anchor attribute changes to another element');
+
+test(() => {
+  document.body.offsetLeft; // Force layout
+  target2.setAttribute('anchor', 'nonexist-anchor');
+  assert_equals(target2.offsetLeft, 123);
+  assert_equals(target2.offsetTop, 456);
+}, 'Layout should be updated when anchor attribute changes to a non-existent element');
+</script>