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);
}