1 files changed, 31 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/browsers/the-window-object/window-indexed-properties-delete-no-cache.html b/testing/web-platform/tests/html/browsers/the-window-object/window-indexed-properties-delete-no-cache.html
new file mode 100644
index 0000000000..22262943aa
--- /dev/null
+++ b/testing/web-platform/tests/html/browsers/the-window-object/window-indexed-properties-delete-no-cache.html
@@ -0,0 +1,31 @@
+<!doctype html>
+<meta charset=utf-8>
+<title>Deletion of WindowProxy's indexed properties is not cached</title>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/window-object.html#windowproxy-delete">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id=log></div>
+<script>
+const iframe = document.createElement("iframe");
+iframe.srcdoc = "";
+
+test(() => {
+  assert_equals(window.length, 0);
+  for (let i = 0; i < 1e5; i++) {
+    assert_true(delete window[0]);
+  }
+
+  document.body.append(iframe);
+  assert_false(delete window[0]);
+}, "Absence of index '0' is not cached");
+
+test(() => {
+  assert_equals(window.length, 1);
+  for (let i = 0; i < 1e5; i++) {
+    assert_false(delete window[0]);
+  }
+
+  iframe.remove();
+  assert_true(delete window[0]);
+}, "Presence of index '0' is not cached");
+</script>