UnitTestViewModel2.cs

public class UnitTestViewModel
{
    public Command LoadDataCommand { get; set; }
    public string Data { get; set; }
    readonly IDependencyService _dependencyService;

    public UnitTestViewModel() : this(new DependencyServiceWrapper())
    {
    }

    public UnitTestViewModel(IDependencyService dependencyService)
    {
        _dependencyService = dependencyService;
        LoadDataCommand = new Command(async () => await LoadData());
    }

    public async Task LoadData()
    {
        Data = await _dependencyService.Get<IDeliverServerSideData>().GetJsonData();
    }
}