@ervan Hmmm. I'd also make sure you don't have order-dependent tests, share file objects, or run specs that mutate your #database (including #PStore with ultra-safe locking) outside of a #DBtransaction you can abandon.

This is less about making the tests parallel or concurrent than about whether you're using #testfixtures that create #Heisenbugs. Using #testfactories, #tempfiles, or an #MVCC #DB could help you a lot there.