How Do You Regression-Test Agents When Every Run Takes a Different Path?

No-Age-3362 · reddit · 2026-09-30

A Reddit discussion on regression-testing agents: unit tests assume deterministic input-output, but agents call three tools on one run and five on the next, both correct. Worse, one run can silently skip a required check while still looking fine.

Partial approaches covered: outcome-only assertions, asserting a few required/forbidden steps (must call X before Y, never call Z), scoring pass rates over multiple runs, and LLM-as-judge on traces. The author asks what teams actually use in production and how many runs per case before trusting a pass rate.

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