1 files changed, 15 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/browsers/browsing-the-web/navigating-across-documents/resources/wait-for-messages.js b/testing/web-platform/tests/html/browsers/browsing-the-web/navigating-across-documents/resources/wait-for-messages.js
new file mode 100644
index 0000000000..62ddec49f1
--- /dev/null
+++ b/testing/web-platform/tests/html/browsers/browsing-the-web/navigating-across-documents/resources/wait-for-messages.js
@@ -0,0 +1,15 @@
+// Asynchronous function that waits for the given number of messages to be
+// received by `window`, then returns those messages.
+function waitForMessages(numMessages) {
+  return new Promise((resolve) => {
+    const messages = [];
+
+    window.addEventListener("message", function handler(evt) {
+      messages.push(evt.data);
+      if (messages.length == numMessages) {
+        window.removeEventListener("message", handler);
+        resolve(messages);
+      }
+    });
+  });
+}