1 files changed, 25 insertions, 0 deletions
diff --git a/testing/web-platform/tests/websockets/bufferedAmount-unchanged-by-sync-xhr.any.js b/testing/web-platform/tests/websockets/bufferedAmount-unchanged-by-sync-xhr.any.js
new file mode 100644
index 0000000000..b247ee56f6
--- /dev/null
+++ b/testing/web-platform/tests/websockets/bufferedAmount-unchanged-by-sync-xhr.any.js
@@ -0,0 +1,25 @@
+// META: script=constants.sub.js
+// META: global=window,dedicatedworker,sharedworker
+// META: variant=
+// META: variant=?wss
+// META: variant=?wpt_flags=h2
+
+async_test(t => {
+  const ws = CreateWebSocket(false, false);
+  ws.onopen = t.step_func(() => {
+    ws.onclose = ws.onerror = null;
+    assert_equals(ws.bufferedAmount, 0);
+    ws.send('hello');
+    assert_equals(ws.bufferedAmount, 5);
+    // Stop execution for 1s with a sync XHR.
+    const xhr = new XMLHttpRequest();
+    xhr.open('GET', '/common/blank.html?pipe=trickle(d1)', false);
+    xhr.send();
+    assert_equals(ws.bufferedAmount, 5);
+    ws.close();
+    t.done();
+  });
+  ws.onerror = ws.onclose = t.unreached_func('open should succeed');
+}, 'bufferedAmount should not be updated during a sync XHR');
+
+done();