Cursor "Iterate Until Tests Pass, Never Touch the Tests"

First-party Cursor guidance for the iterate-until-green loop, with the key anti-reward-hacking clause: the agent may never modify the tests it is trying to satisfy. Works in Cursor, Claude Code /goal, and Codex.

Implementation note

When to use: any test-driven agent session where the tests define done — you have a failing suite (TDD-style or a regression pile) and want the agent iterating until green without the classic cheat. How it works: the instruction is a plain contract: write code that makes these tests pass, do NOT modify the tests, and keep iterating — run the suite, fix failures, run again — until all tests pass. This is first-party Cursor guidance from their agent best-practices, and the pattern translates directly to Claude Code /goal and to Codex. Safety: the never-touch-the-tests clause is the entire anti-reward-hacking rail — without it, the cheapest path to green is editing an assertion, and agents find cheap paths. State it explicitly every time. The residual check is yours: confirm at the end that the test files are untouched (a quick git diff on the test paths) and that the implementing code is honest.

Source: Cursor blog ↗

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