It sounds like the problem was not your ability to debug ruby code to but your reaction to them asking you to do it. You almost sound outraged that they dared to ask you to debug some ruby code. A better candidate would have just calmly proceeded to have a go at it while explaining their thought processes to the interviewer, even if they had never coded in ruby or whatever language.
"Outraged" is overstating it, but yes, I was pretty annoyed, but not because they asked me to debug Ruby code. I was annoyed because they lied to me. If they'd just been up front and told me they really were just looking for Ruby programmers I could have told them sorry, I am not your man, and saved everyone a lot of time.
That's a bit of an overstatement, chances are there was a miscommunication and the person interviewing you did not know that you had been told there would be a know ruby questions. Seriously, its just an interview, they're not going to go out of their way to accomodate your every request, just roll with it. Since you were able to debug the ruby code, its sounds like you could have gotten the job if it wasn't for your attitude. IMO the right attitude is more important than raw technical skill, you might pass the "Can he code in ruby?" part of the interview, but fail the "Can he handle things not going his way?" part.
I recently had an interview for a developer job where I was asked lots of devops questions, even though it wasn't a devops-heavy role and I don't have much devops experience listed on my CV. I wasn't able to answer many of the questions but I drew on what little knowledge I did have to try and come up with answers. In the end I got the job because the interviewer said he appreciated how I tried to reason out answers to his questions even without much knowledge in the area. If I would have gotten all annoyed and started acting like I was being lied to and cheated then I doubt I would have gotten the job.
With all due respect I think I'm in a better position to judge that than you are. But there are two things you should know. First, I haven't told you the whole story (and I'm not going to). And second...
> the person interviewing you did not know that you had been told there would be a know [sic] ruby questions
The conversation went something like this:
Him: Welcome, the first thing we want you to do is debug this Ruby code. (Actually, the first thing he wanted me to do was copy-and-paste some shell commands from an unfamiliar text editor into a shell window, but that's another story.)
Me: Um, OK, but I've never worked in Ruby, and I told that to everyone I spoke to on the phone screen because I know you're a Ruby shop.
Him: Yeah, I know. But this is what we want you to do.
Me: OK, I'll give it my best shot, but don't expect too much.
Ok, so that conversation sounds pretty reasonable, you said "OK, I'll give it my best shot, but don't expect too much.", then proceeded to give it a shot and actually succeeded at debugging it. So... whats the problem?
Like I said: the problem is that they lied to me, and as a result they made me waste a day of my life [1]. If I'd known that this was going to happen, I could have either brushed up on my Ruby, or (more likely) cancelled the interview because I would have known ahead of time that I would not be a good fit for their company. There is a reason I've never used Ruby, and it's not that I've never had the chance. I told them that, and they said it would not be a problem. But it was.
[1] Actually, it was only half a day because they cancelled the interview after two hours. Like I said, I have not told you the whole story, and I'm not going to. But the whole thing was a train wreck from beginning to end.
Maybe they were curious about how someone who has never worked with Ruby (but has tons of related experience otherwise) would fare with it. Or, curious how grokkable their particular code is to non-Rubyists.
