public async Task GetAlbumPhotosAsync_AlbumDoesNotExist_NotFound() { _albumServiceMock.Setup(x => x.GetAlbumPhotosAsync(200)) .ReturnsAsync(null as IEnumerable <Photo>); var actionResult = await _albumController.GetAlbumPhotosAsync(200); var notFoundResult = actionResult as NotFoundResult; Assert.IsNotNull(notFoundResult); Assert.AreEqual(StatusCodes.Status404NotFound, notFoundResult.StatusCode); }