How do you early playtest things at scale effectively?

Before the game is ready for a real playtest with real players, if you just want to test out some basic mechanics and make sure they work right and balance them....what's the best method?

I figure I could get a few friends and actually playtest specific mechanics repeatedly but that would be the most boring and time consuming.

I could also hand roll things myself over and over, but that would also be tedious and time consuming.

I might know enough to write a simple program that could test some things out, but the complexity could be an issue. It's also harder to account for human decision making.

Right now I mostly want to test out my basic weapons against each other and make sure their strengths and weaknesses seem to be working correctly.