The WTF test has been used, in variations, for many purposes. Paul Lamere gives the test its formal name (he is not the first to do so, but may be the one who makes the name stick) in applying it to a very particular question. In his blog, he writes:
there is something that we can do that is fairly easy to give us an idea of how well a playlisting engine works compared to others. I call it the WTF test. It is really quite simple. You generate a playlist, and just count the number of head-scratchers in the list. If you look at a song in a playlist and say to yourself ‘How the heck did this song get in this playlist’ you bump the counter for the playlist. The higher the WTF count the worse the playlist.
The WTF test is a variant of the Plausibility Test, without which it is possible humanity would not have survived as long as it has, given the large number of implausible things foisted upon us every day by so many fervent foisters.
(Thanks to investigator Thierry Bertin-Mahieux, who works with Lamere, for bringing this to our attention.) The image below is part of one of the many playlists Lamere created and WTF-tested: