I would be much happier if the interviewer gave me a small app to create from home (which was relevant to the work they actually do) & then discuss my implementation choices in person with them.
What is the point of having me spend most of an interview doing things with dijkstra's algorithm if never, in the history of your company has this been used nor do you plan to use it & then spend the last 5 minutes asking a few vague questions about what I like about Ruby / hate about Rails.
Technical tests, in my experience, are mostly (90%+ of the time) composed of challenges which have no relevancy to the work I would be doing for that company, its pointless ceremony over common sense.