I was reading Scott Hanselman's blog today and ran across this post which is actually his refferal to the site for this post from Patrick Cauldwell's blog. Both are discussing how to use external files as part of your Unit Testing in NUnit.
As pointed out by Patrick, using paths to reach such files is problematic as the file's location may shift from your box to a build box, etc. So the perfectly elegant solution that has been devised by Patrick is to create such files as Embedded Resources in your testing project. You can then access that file as a stream, and write it out to a known position (such as a temp directory) for your tests to use.
Pretty slick ... need to write the VB 'conversion' here shortly.