Coding agents weaken tests about as rarely as humans do, study finds

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A developer built honest-ci, a GitHub Action that flags pull requests which delete, skip, or rewrite tests for human review. Analyzing 1,598 agent-opened and 1,119 human-opened public PRs from July and August 2026, the author found test changes occurred in roughly one in eleven PRs for both groups, at 8.4% for agents and 10.4% for humans. Most flagged changes had a stated justification, such as a removed feature or a genuinely changed expected value. Test weakening with no explanation was rare for both, at 0.3% for agents and 0.5% for humans, and the confidence intervals overlapped. The study's detector uses five deterministic checks on the full diff, so distinguishing legitimate removals from problematic ones still depends on human review.

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