SMC (State Machine Compiler) is worth bringing up here, which uses a formal language to define a state machine and produces code in one of a dozen+ languages to run it. Makes it impossible to build a bad state machine. I remember using this on some small projects last decade, I'm happily surprised to see it's still maintained.

http://smc.sourceforge.net/ and code at: https://sourceforge.net/p/smc/git-code/ci/master/tree/