Recently I come across a codebase where we spent days breaking dependencies and writing tests for a single class before we could make a change. Even more frustratingly, despite our efforts to take small steps and use well established dependency breaking techniques, we still almost leaked a serious bug into production.

So started to wonder if modern language features and tooling could make this hurdle unnecessary?

At answer I came up with is SpecRec: tool that generates characterisation tests with minimal code interventions. I’ll walk through the technique, show a real‑world use case, and explain how you can adopt it in your own projects.