public void allDevicesShouldHaveDiskSize() { tokenSource = new CancellationTokenSource(); Assert.DoesNotThrow(() => { var tsk = engine.BuildDevicesAsync(tokenSource.Token); tsk.Wait(); devColl = tsk.Result; }); devColl.AsParallel().ForAll(dev => { System.Diagnostics.Trace.WriteLine("Device " + dev.FriendlyName + " size is: " + (dev.DiskSize.HasValue == true ? dev.DiskSize.Value.ToString() : "<empty>")); }); var zz = devColl.Where(dev => !(dev.DiskSize.HasValue && dev.DiskSize.Value >= 0)); Assert.True(zz.Any() == false); }