Me [21 F] and my bf [21 M]: Haven't argued in over a year of dating, am I crazy for wanting to?

I have been with my boyfriend 'Alex' for a year and two months. We have been long-distance for pretty much the entire time and we get to visit each other once every 3-5 months. We also make time to Skype each other once a week and text 5 or 6 times throughout the day. We're seriously committed and talk about getting married someday, but we both want to go to grad school and have stable jobs first.

The time I have spent with Alex has been wonderful. We recently took a 3-day trip to a vacation spot a 5 hour drive away from where I live. No bickering, no awkward or extended lulls in conversation, everything went off without a hitch. We even got lost a few times and we both kept a level head. I feel good about the way we treat each other and I would consider this the healthiest relationship I've been in.

My mother told me years ago that, before you decide to marry someone, you should see how they treat you when they're drunk and how they treat you when they are angry. Alex and I have been drunk together on several occasions (in person and over Skype) and we mostly just get giggly and more affectionate.

To date, Alex and I have never had a serious fight. (I got snappy with him once or twice and immediately apologized because I felt bad. He was understanding and didn't react or retaliate) I am not complaining at all, but I want to know what to expect when any anger is directed at me. I have never seen him angry in person, though I have comforted him over the phone and as far as I can tell he manages his anger pretty well. I have no reason to believe that an argument between us would be any different, but I want to be sure before we commit long-term.

Part of the reason I'm so concerned about this is because Alex told me a few months ago that he was diagnosed with Bipolar Disorder when he was in high school (not sure the type, this was before DSM V) He stopped taking his medication a few months after receiving the diagnosis and prescription because he didn't like how he felt when he took them. He has been unmedicated for the entire time we've been dating and everything is going great, but I understand that BPD's 'thing' is the back-and-forth of mania and depression. I don't like that I'm basing this concern more off of a diagnosis than the actual time we've spent together, but I hear all sorts of horror stories about people changing once they get married. I hope I don't sound awful for being so cautious, but I want to make sure that I know what to expect and if/how I can help.

As mean and messed-up as it sounds, I want us to have a fight before we marry to see what I can expect. I don't want to do something silly or sitcom-esque like bait him into a fight or start something on purpose. Is there another way to assess this and see what I can expect from Alex when he's angry?

TL;DR: In a stable, happy relationship and haven't fought once over the last year and few months. BF has BPD and I want to make sure I see him angry before marriage/long-term commitment so I know what to expect. Short of starting a fight for no reason, how can I assess this?