This upload demonstrator has files prefilled from the "serverside" (mocked via javascript)
It also has some in page source javascript that enables / disables the submit button if the upload list
contains files with errors (this behaviour is entirely up to you to control, depending on your UX demands)
In order to simulate an upload you can remove the erroneous files and click upload (to get the list of files
that needs uploading)
You can set the actions and groups through element.actions / element.groups instead of directly on the
element as shown here