Via John Gruber, here is a honest-to-God example of how not to design a user interface. Feast your eyes upon this screenshot of a Windows based “Bulk Renaming Utility”.

What’s more awesome than a screenshot like that? How about some quotes from the tutorial:

Ok, here’s Bulk Rename Utility (BRU) from the start. You’ve installed the software, you’ve launched it, and you now see a million and one controls and boxes on the screen. The first thing to do is DO NOT PANIC! [emphasis theirs]

[..]

Okay, now here’s a simple example. You want to replace all underscores (_) in a filename with spaces. So, all you do is this: In Group 3 (called Repl. (3) ) simply enter an underscore in the Replace box, and enter a space in the With box. Then highlight all your filenames (mouse, keyboard, Ctrl+A etc.). In the “New Name” column you will see what the new name is going to look like, for each and every file you have selected.

Now imagine designing tests for that user interface. Your head a splode.