Ossature 0.2 adds VMD, a spec file of test cases you write yourself. The model that generates the code never sees the expected values, so the code can't be generated to fit them. Also in 0.2, editing one spec no longer rebuilds its dependents when the interface between them is unchanged.
The 0.1 releases let an AMD component declare how its code should behave, and add a reviewer that reads the generated code against those contracts after it compiles.
The format you pick for specs is the easy part. The hard part is knowing what is worth writing down and having a good harness around it that helps you without being in your way. A few practical principles for writing specs that an LLM can actually build from, with a small example.
Generated code does roughly what you asked, but you can't tell from reading it which decisions were deliberate and which the model just guessed. Specs are where those decisions go so they don't end up living only in the generated source.
Ossature is an open-source harness for spec-driven code generation. Write specs, validate, audit, review the build plan, and generate code with full control at every step.