File posts in integration test

It seems that my file data is being treating as a string or something.
Has anybody been able to do a file post in an integration test?

NoMethodError (undefined method `original_filename' for "#<File:
0x316c300>":String):
    /app/models/attachment.rb:21:in `file='
    /vendor/rails/activerecord/lib/active_record/base.rb:1846:in
`send'
    /vendor/rails/activerecord/lib/active_record/base.rb:1846:in
`attributes='
    /vendor/rails/activerecord/lib/active_record/base.rb:1845:in
`each'
    /vendor/rails/activerecord/lib/active_record/base.rb:1845:in
`attributes='
    /vendor/rails/activerecord/lib/active_record/base.rb:1672:in
`initialize'
    /app/models/attachment.rb:11:in `initialize'

Actually, I just found this workaround to a rails bug:

http://dev.rubyonrails.org/ticket/4635