If you happen to be coding in Rust, for really robust concurrency testing, I cannot recommend enough the AWS Shuttle library (https://github.com/awslabs/shuttle) which can find insanely complicated race conditions.

What the Shuttle library is doing is basically automatically going through all the permutations of the schedule diagrams described int his blog post.

We used it at AWS to verify the custom filesystem we wrote to power AWS S3.

If you're curious, I wrote a little tutorial on it here: https://grantslatton.com/shuttle