1 files changed, 23 insertions, 0 deletions
diff --git a/testing/web-platform/tests/portals/resources/portal-post-message-after-activate-window.html b/testing/web-platform/tests/portals/resources/portal-post-message-after-activate-window.html
new file mode 100644
index 0000000000..73d2c11558
--- /dev/null
+++ b/testing/web-platform/tests/portals/resources/portal-post-message-after-activate-window.html
@@ -0,0 +1,23 @@
+<!DOCTYPE html>
+<body>
+  <script>
+    var portal = document.createElement("portal");
+    portal.src = "portal-post-message-portal.html";
+    document.body.appendChild(portal);
+
+    portal.onload = () => {
+      portal.activate().then(() => {
+        error = "";
+        try {
+          portal.postMessage("message");
+        }
+        catch(err) {
+          error = err.name;
+        }
+        bc = new BroadcastChannel("portals-post-message-after-activate");
+        bc.postMessage(error);
+        bc.close();
+      });
+    }
+  </script>
+</body>