Testing AI Applications with Microsoft.Extensions.AI.Evaluation for Reliable Software
Developer & Versioning Note: This post reflects the Microsoft.Extensions.AI.Evaluation experience as documented in late 2025. APIs, evaluators, and scoring behavior can change across releases and providers. This is informational only (not professional advice). Please validate results in your own environment; deployment decisions and risk remain with your team. AI features don’t fail like normal features. Your code compiles, the endpoint is up, the UI looks fine—and then the model answers the same question two different ways on two different days. That’s not a “bug” in the classic sense. It’s the nature of probabilistic systems. And it’s exactly why evaluation (evals) has become the missing piece between “cool demo” and “reliable software.” Microsoft.Extensions.AI.Evaluation is Microsoft’s attempt to make evals feel like normal .NET testing: code-first, DI-friendly, and something you can run in Test Explorer or in a pipeline without inventing an entire framework ...