1 files changed, 30 insertions, 0 deletions
diff --git a/testing/web-platform/tests/browsing-topics/resources/permissions-policy-util.sub.js b/testing/web-platform/tests/browsing-topics/resources/permissions-policy-util.sub.js
new file mode 100644
index 0000000000..e8bf45049c
--- /dev/null
+++ b/testing/web-platform/tests/browsing-topics/resources/permissions-policy-util.sub.js
@@ -0,0 +1,30 @@
+const TOPICS_PERMISSIONS_POLICY_ERROR_MESSAGE = 'The \"browsing-topics\" Permissions Policy denied the use of document.browsingTopics().';
+
+function test_topics_feature_availability_in_subframe(test, is_same_origin, expect_feature_available_func) {
+  const same_origin_src = '/browsing-topics/resources/document-api-notify-parent.tentative.https.html';
+  const cross_origin_src = 'https://{{domains[www]}}:{{ports[https][0]}}' +
+    same_origin_src;
+
+  let frame = document.createElement('iframe');
+  frame.src = is_same_origin ? same_origin_src : cross_origin_src;
+
+  window.addEventListener('message', test.step_func(function handler(evt) {
+    if (evt.source === frame.contentWindow) {
+      expect_feature_available_func(evt.data);
+
+      document.body.removeChild(frame);
+      window.removeEventListener('message', handler);
+      test.done();
+    }
+  }));
+
+  document.body.appendChild(frame);
+}
+
+function expect_topics_feature_unavailable(data) {
+  assert_equals(data.error, TOPICS_PERMISSIONS_POLICY_ERROR_MESSAGE);
+}
+
+function expect_topics_feature_available(data) {
+  assert_equals(data.error, 'No error');
+}