public async Task DownloadFile()
{
var mock = new Mock <IWebClientHelper>();
var timeline = new TimelineService(BaseUrl, "ABC", "123", "cache", mock.Object);
await timeline.DownloadFileAsync("http://www.upload.com/url", "testfilename.docx");
mock.Verify(m => m.DownloadFileAsync("http://www.upload.com/url", "testfilename.docx"));
}