Create filesystem repository instance Create subfolders, place image and non-image files in it Browse filesystem repository in filepicker (for example in Private files) and make sure thumbnails and images dimensions are displayed. Check different view types in filepicker - icons, list, table Replace one of the images with a different image with the same name Make sure the thumbnail is updated Copy thumbnail url, logout or login as user who can not see this filesystem repository, make sure you can not view image. Run cron, make sure the message appears that X thumbnails were deleted (note that each modified/deleted file may have 'thumb' and 'icon' thumbnails generated)