#[tokio::test]
async fn hid_roundtrip() {
    use lesavka_common::lesavka::*;
    use lesavka_server::RelaySvc;           // export the struct in lib.rs
    let svc = RelaySvc::default();
    let (mut cli, srv) = tonic::transport::Channel::balance_channel(1);
    tokio::spawn(tonic::transport::server::Server::builder()
        .add_service(relay_server::RelayServer::new(svc))
        .serve_with_incoming(srv));

    let (mut tx, mut rx) = relay_client::RelayClient::new(cli).stream().await.unwrap().into_inner();
    tx.send(HidReport { data: vec![0,0,4,0,0,0,0,0] }).await.unwrap();
    assert!(rx.message().await.unwrap().is_none());   // nothing echoed yet
}