What would be an idiom or word or name for someone that is an initial tester (like a beta tester).
I am writing a speech for my younger brother's engagement and want to say how I have always been the first to try everything in my family--schooling, learning to drive, college applications, etc.--because I was the oldest son. My parents basically used me as a trial run to test the waters each step of the way in their parenting. They tweaked and refined the process with each of my two brothers.
Now for his wedding, he's being sent out to scout for the proverbial mines for the first time.
So I'm looking for a better term than beta tester to describe what I have been my entire life. I was kind of like a "lab rat", but that sounds horrible. Here's the line:
"Throughout our life, being the oldest, I was sent out as the front line to test the waters."
I really hate that line. I hope having a better term for "beta tester" would make that line make more sense and sound better.