Testing ServiceController Class

Im working on a small desktop app which controls services on a server. For controlling services i am using ServiceController class. What i want to do is; testing my code and abstract the ServiceController class from my code. So i did something like below.

  public interface IServiceControllerWrapper
{          
    string ServerNameOrIP { get; }    
    int Status { get; }
    bool CanStop { get;  }       
    void StartService();

}

 public class ServiceControllerWrapper : IServiceControllerWrapper
{
    ServiceController _controller;
    const string ServiceName = "W3SVC";


    public ServiceControllerWrapper(string serverNameOrIP)
    {
        _controller = new ServiceController(ServiceName, serverNameOrIP);
    }     


    public string ServerNameOrIP { get { return _controller.MachineName; } }

    public int Status
    {
        get
        {
            switch (_controller.Status)
            {
                case ServiceControllerStatus.ContinuePending:
                case ServiceControllerStatus.PausePending:
                case ServiceControllerStatus.Paused:
                    return 4;
                case ServiceControllerStatus.StopPending:
                case ServiceControllerStatus.Stopped:
                    return 0;
                case ServiceControllerStatus.StartPending:
                case ServiceControllerStatus.Running:
                    return 1;
                default:
                    return -1;
            }
        }
    }


    public bool CanStop
    {
        get
        {
            return _controller.CanStop;
        }
    }

    public void StartService()
    {
        _controller.Start();
    }

   //shortened

}

and i am using this class within another named ServerContext. Implementation is;

   public interface IServerContext
{
    string ServerName { get; }
    IServerContext Parent { get; }       
    IServiceControllerWrapper Controller { get; }
    bool HasError { get; set; }
    int GetServiceStatus();       
}

  public class ServerContext : IServerContext
{
    IServerContext _parent;
    IServiceControllerWrapper _controller;     


    public ServerContext(IServerContext parent, IServiceControllerWrapper wrapper)
    {
        _parent = parent;
        _controller = wrapper;
    } 


    public string ServerName { get { return _controller.ServerNameOrIP; }}

    public IServerContext Parent
    {
        get
        {
            return _parent;
        }          
    }

    public IServiceControllerWrapper Controller
    {
        get
        {
            return _controller;
        }
    }

    public bool HasError { get; set; }


    public int GetServiceStatus()
    {
       return _controller.Status;
    }        

 }

My question here is, i am tryint to test ServerContext and ServiceControllerWrapper but i cant manage to create fake objects. this test method always throws exception because ServerName is null.How can i arrange this code to pass test and or how can i test those classes?

      [Fact]
    public void ServerName_CannotBeEmpty()
    {
        Mock<IServiceControllerWrapper> _controller = new Mock<IServiceControllerWrapper>();
        ServerContext serverContext = new ServerContext(null, _controller.Object);
        //this code fails. 
        serverContext.ServerName.Should().Not.Be.NullOrEmpty();
    }

Any suggestions are welcome. Note: i am using moq,xunit and SharpTestsEx libraries for testing.