Visual Studio Tests and "The location of the file or directory xxx is not trusted"

If you've ever downloaded stuff from the internet (from XP SP2 onwards), you'll know that the OS marks the file as un-trusted and that to use it you need to right-click, go to properties and click "Unblock".  If you download a zip and extract it's contents without having unblocked the zip, then you probably also know that every extracted file will also be marked as un-trusted. 

Referencing a file from an un-trusted source within Visual Studio (for example, adding a reference to the latest library that you've just downloaded) will work just fine, but when you try to run your unit tests they will barf with a "location of the file or directory is not trusted" error.

The top tip is to remember to unblock the zip file before doing the extract; that way, all the files that you extract will also be unblocked and the world will be a happy place (assuming that none of them have viruses, trojans etc!)

If you forget, and if you've now got files scattered all over your project such that deleting them and re-extracting is a pain, then here's another option - ZoneStripper is a handy command-line tool that can run recursively over a directory and get rid of the blocks.  Works like a treat.