> It shouldn't need to be run from `test/threadsafety`

Not sure where you got that, this script runs fine from any directory.

> I really don't want this to be a bash file.

I will rewrite it in ruby so that it is using a technology you find more comprehensible.

> It would also be nice to merge it into multi_threaded_runner.rb;

I agree. This is how I started, I tried to do it using fork, but ran into issues in jruby where fork is not supported. After spinning my wheels for a while I decided to change tack. But I will try again using a `system()` call instead of fork.