  void expectHandshakeSuccess() {
    EXPECT_FALSE(client->except.hasValue())
        << "client handshake error: " << client->except->what();
    EXPECT_FALSE(server->except.hasValue())
        << "server handshake error: " << server->except->what();
  }
  void expectHandshakeSuccess() {
    EXPECT_FALSE(client->except.hasValue())
        << "client handshake error: " << client->except->what();
    EXPECT_FALSE(server->except.hasValue())
        << "server handshake error: " << server->except->what();
  }