Quint
Quint, an executable specification language for reliable systems
Quint is an executable specification language with delightful tooling, designed for distributed systems and based on the temporal logic of actions (TLA). Write specifications you can run, simulate, and verify, so subtle bugs get caught before reaching production. Quint is open source (Apache 2.0) and developed by Informal Systems. Source code and documentation live on GitHub and quint.sh.