message: Old clippy/rust doesn't like that
diff: @@ -1849,9 +1849,11 @@ impl Connection {
  .write_frames(TransmissionPriority::Low, builder, tokens, stats);
  #[cfg(test)]
  + {
  if let Some(w) = &mut self.test_frame_writer {
  w.write_frames(builder);
  }
  + }
  Ok(())
  }
  