public void AddDownload()
{
var ds = new DownloadService(null);
var download = new Mock <IDownload>();
var state = DownloadState.Queued;
download.Setup(d => d.State).Returns(() => state);
download.Setup(d => d.Progress).Callback(() => state = DownloadState.Downloading)
.Returns(Observable.Empty <DownloadProgress>());
ds.Add(download.Object);
download.Verify(d => d.Start(null), Times.Once);
}
