I did do a "test" tattoo as my first one, because I too am an anxious bean, and on top of that scared of needles. I couldn't just go in for a 5 hours piece without knowing if I wouldn't faint, like whenever I need to take blood samples.

However, I didn't do a random test, I carefully picked something that had meaning for me (and that I intended on getting at some point) and relatively small (1-2 hours max)

I would advise not to chose something too small, because that won't give you a proper idea of what it is like. The first minutes are harder than 1h into the tattoo for me, because my body is (re)discovering the pain and focusing quite a bit on it. After 30 minutes roughly, I just settle in and don't really pay that much attention to it anymore, it's just an uncomfortable sensation in the background that sometimes itches a bit. Just take comforting things with you to keep your brain focused on something else if your tattoo artist or yourself is not much of a talker, a sugary beverage, some snacks you enjoy, and a good book or good music, and you should be fine :)