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property-test-authoring

Use when authoring property tests, assessing PBT fit for a code path, reviewing existing property tests, or triaging a failing counterexample. Not for test-first features: use tdd.

.devin/skills/property-test-authoring/SKILL.md

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# Property test authoring

## Contract

| Field | Bound contract |
|---|---|
| Trigger | The user asks to add or improve generated property tests for an inverse, invariant, oracle, idempotence rule, parser, normalizer, algorithm, data structure, or smart-contract state machine; to decide whether property-based testing fits a code path; to review existing property tests; or to classify a failing counterexample. |
| Authority | Reversible local: mode author writes only property tests to local files tracked by version control, plus user-approved production-code seams; modes assess, review, and triage write nothing; rollback is `git revert` or `git checkout` of the touched file. No remote mutation. |
| Side effect | Mode author writes property tests in the existing framework and adds a testing dependency or production-code seam only with user approval. Modes assess, review, and triage return chat output only. |
| Done | Mode author: the strongest grounded property is encoded with domain-aware generators and pinned edge cases, and the targeted run passes while a plausible contract violation fails it. Mode assess: a verdict names property, domain, strategy seam, and library, or declines to example tests. Mode review: every test is classified against the defect taxonomy with evidence, severity, and the strongest replacement property. Mode triage: the counterexample is classified with cited evidence and a minimal repair. |

## Inputs

- Mode: `author` (default), `assess`, `review`, or `triage`. Inferred from the request when not stated.