Comment by exabrial

> Fray is a concurrency testing tool for Java that can help you find and debug tricky race conditions that manifest as assertion violations, run-time exceptions, or deadlocks. It performs controlled concurrency testing using state-of-the-art techniques such as probabilistic concurrency testing or partial order sampling.

> Fray also provides deterministic replay capabilities for debugging specific thread interleavings. Fray is designed to be easy to use and can be integrated into existing testing frameworks.

I wish I had this 20 years ago.