I was having difficulty setting the $_FILES and $_POST parameters in a way that didn't make Forge grumpy.  I tried setting all five (name, tmp_name, size, error, type), making sure files were in the file system where they should be, but it still didn't like it.  Do you have any recommendations on how to do this?

In any case, after fighting with it for quite awhile, I finally realized what I really *wanted* to test here was the logic downstream of the validation logic anyway, and so did this.  If you have a pointer or two on how to correctly upload the file in a way that keeps Forge happy, then I could remove this...