Microsoft has a library/tool called Coyote* that helps with testing distributed systems; you can write tests/specifications, Coyote will systematically explore nondeterminism in your system and check if your tests still pass. If there's a failure, it'll show the sequence of events that led to the failing test.

I started a project to implement Raft with a KV-store on top, similar to the article, meaning to use Coyote to test it; I didn't get that far before losing interest, though. It's reassuring to read that it took Phil several months to write the code in the post, it's good to know that this is a decidedly nontrivial problem.

* https://github.com/microsoft/coyote