sferik/rails_admin — pull request #1497 by fernandomm (2013-01-28 20:53:12+00:00)
Title: Fixes issue #1446 by checking file type with filemagic gem.

It adds an extra dependency but seems to work fine.

If you think this is good, do you mind telling me where should i place the specs for this change?

I haven't found too much references to "file uploads" but maybe spec/integration/basic/list/rails_admin_basic_list_spec.rb is a good one?