Evaluate non-deterministic LLM/AI output with evals instead of one-shot "it worked" — define expected behavior first, measure pass@k / pass^k, and grade with code / model / human graders. Use when building or changing an AI/LLM feature, an agent, a prompt, a RAG pipeline, or a classifier, where a single good run is not proof of correctness. Complements writing-tests (deterministic logic) and developing-features-tdd.
