1 files changed, 21 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/browsers/the-windowproxy-exotic-object/windowproxy-prevent-extensions.html b/testing/web-platform/tests/html/browsers/the-windowproxy-exotic-object/windowproxy-prevent-extensions.html
new file mode 100644
index 0000000000..97a156290a
--- /dev/null
+++ b/testing/web-platform/tests/html/browsers/the-windowproxy-exotic-object/windowproxy-prevent-extensions.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>[[PreventExtensions]] on a WindowProxy object should return false</title>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/window-object.html#windowproxy-preventextensions">
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+
+<script>
+"use strict";
+
+test(() => {
+  assert_throws_js(TypeError, () => {
+    Object.preventExtensions(window);
+  });
+}, "Object.preventExtensions throws a TypeError");
+
+test(() => {
+  assert_false(Reflect.preventExtensions(window));
+}, "Reflect.preventExtensions returns false");
+</script>