Using string instead of constant for describe argument causes data leakage

[jasonswett]

I created a repo here which reproduces the bug and gives reproduction instructions. I imagine that that's a sufficient explanation, but if not, I'm happy to explain further!

I'm happy to try to diagnose/fix as well but I wanted to get this issue opened as a first step and I haven't yet dived into the code for minitest-spec-rails to see what the cause might be.