Systemd service from configuration is not created

Given the following configuration.nix:

{lib,...}:{
  containers=rec{
    node1={
      privateNetwork=true;
      hostAddress="192.168.0.10";
      localAddress="192.168.0.11";
      config=let
  p=(import ./default.nix ).tesi;
in{
  environment.systemPackages=[p];
  services.openssh.enable=true;
  systemd.services.testing=rec{
    wantedBy=["multi-user.target"];
    requiredBy=wantedby;
    before=wantedby;
    systemConfig.ExecStart="${p}/bin/test-chat";
  };
};
    };
    node2=node1//{
      
      hostAddress= "192.168.0.20";
      localAddress="192.168.0.21";
    };
    node3=node1//{

      hostAddress= "192.168.0.30";
      localAddress="192.168.0.31";
    };

  };
}

After sudo nixos--shell -v(from https://github.com/wavewave/nixos-shell/tree/submodule )
inside the shell I do

systemctl cat testing
No files found for testing.service.

What am I doing wrong?