Force the LLM to write property-based tests (depends on the language you use whether or not good libraries are available -- but if they are available 100% make

Force the LLM to write property-based tests (depends on the language you use whether or not good libraries are available -- but if they are available 100% make use of them). Iterate with the LLM on the invariants. Forcing the discussion of invariants, and property-based testing -- seems to improve on the issues you're mentioning (when using e.g. Opus 4), especially when combined with the "use the public API" or interface abstractions.