public void Videocontroller_WhenVideoExist_ShouldReturnVideoStream() { var mock1 = new Mock <IHostingEnvironment>(); var mock2 = new Mock <IVideoService>(); var mock3 = new Mock <IMapper>(); var mock4 = new Mock <IOptions <AppSettings> >(); var mock5 = new Mock <ILogger <VideoController> >(); // Mock the method of the service var f = GetFileStream(); mock2.Setup(p => p.GetVideoById("1")).Returns(f); VideoController videoController = new VideoController(mock1.Object, mock2.Object, mock3.Object, mock4.Object, mock5.Object); // Act var response = videoController.GetVideoById("1"); // Assert Assert.NotNull(response); Assert.IsType <FileStreamResult>(response); Assert.Equal(31327, ((FileStreamResult)response).FileStream.Length); }