functional est for attachment download

I have written an action for converting attached MS word document files
into a plain text and HTML format. The converted file is then rendered
in a web browser. How can I write a functional test for this action? I
am not confused about creating a fixture for this. (attached MS word
document files are stored as a BLOB in MySQL).

Well I wouldn't really have thought those belonged in a controller
rather than some sort of model but I would start with some sample
files, the expected text or HTML output and assert that converting the
samples created that output