public async Task ExportResultsAsync(ExportFormat format)
 {
     if (IsBusy)
     {
         return;
     }
     IsBusy = true;
     try
     {
         var fileName = _shell.SelectedWriteFile("Select the exported file", "CSV files (*.csv)|*.csv|All files (*.*)|*.*", ".csv");
         if (string.IsNullOrWhiteSpace(fileName))
         {
             return;
         }
         var results = TestResults.Select(r => r.Result).ToList();
         using (var stream = System.IO.File.Create(fileName))
         {
             await Task.Run(() =>
             {
                 _engine.ExportTests(results, stream, format);
             });
         }
     }
     finally
     {
         IsBusy = false;
     }
 }