1 files changed, 34 insertions, 0 deletions
diff --git a/testing/web-platform/tests/css/css-scroll-anchoring/anonymous-block-box.html b/testing/web-platform/tests/css/css-scroll-anchoring/anonymous-block-box.html
new file mode 100644
index 0000000000..97542e2613
--- /dev/null
+++ b/testing/web-platform/tests/css/css-scroll-anchoring/anonymous-block-box.html
@@ -0,0 +1,34 @@
+<!DOCTYPE html>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<style>
+
+body { height: 2000px; margin: 0 10px; }
+#before, #after { height: 100px; }
+#before { margin-bottom: 100px; }
+#container { line-height: 100px; vertical-align: top; }
+
+</style>
+<div id="container">
+  <div id="before">before</div>
+  <span id="inline">inline</span>
+  <div id="after">after</div>
+</div>
+<script>
+
+// Tests anchoring inside an anonymous block box. The anchor selection algorithm
+// should descend into the children of the anonymous box even though it is fully
+// contained in the viewport.
+
+test(() => {
+  document.scrollingElement.scrollTop = 150;
+
+  var span = document.querySelector("#inline");
+  var newSpan = document.createElement("span");
+  newSpan.innerHTML = "inserted<br>";
+  span.parentNode.insertBefore(newSpan, span);
+
+  assert_equals(document.scrollingElement.scrollTop, 250);
+}, "Anchor selection descent into anonymous block boxes.");
+
+</script>