ThreatSpec is an open source project that aims to close the gap between development and security by bringing the threat modelling process further into the development process. This is achieved by having developers and security engineers write threat specifications alongside code, then dynamically generating reports and data-flow diagrams from the code.
Security testing is shifting left, from annual pentests to the realm of unit testing and test-driven development, by taking advantage of automation and agile practices. ThreatSpec is an attempt to continue the evolution.
Check out the Getting Started section on https://threatspec.org/#gettingstarted
Documentation can be found here: https://github.com/threatspec/threatspec/wiki
Checkout out the reference implementation written in Python: https://github.com/threatspec/pythreatspec
Other implementations can be found in the Tools section of the documentation: https://github.com/threatspec/threatspec/wiki/Tools