I actually think that's a really good idea because it allows you to hone your skills without the pressure. I've sometimes considered doing it myself.I would have walked out. I was looking for a job when I was in a job I did not mind but wanted to better myself, so I had quite a few interviews.
A colleague of mine used to go for interviews on a semi regular basis, not because he wanted to leave but because he wanted to use it as leverage to get a pay rise or make other demands. It was your classic "these employers are biting my hand off, but I'd love to stay here, so how about we discuss what you'll do to keep me?" scenario. Obviously he didn't use those exact words, but that was the gist of it. The annoying thing was it worked.
He did eventually leave when he was headhunted by a manager who had recently left. Few of us were sorry to see the back of him.