# Property Test > Design and implement property-based tests that verify invariants across randomized inputs. Use when user says "property test", "invariant test", "fuzz inputs", or wants to discover edge cases that example-based tests miss. Use when this capability is needed. - Skill: `tomevault-io/property-test` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/property-test` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/property-test/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/property-test --- Design and implement property-based tests for the specified target. ## Context Existing test framework: !`ls jest.config* vitest.config* pytest.ini pyproject.toml Cargo.toml 2>/dev/null | head -5` ## Target: $ARGUMENTS ## Instructions 1. Analyze target code and identify algebraic properties (roundtrip, idempotency, invariants, etc.) 2. Design generators for input types 3. Implement property tests using the project's framework 4. Run tests and verify all properties hold 5. Report any counterexamples found --- > Source: [gr1m0h/dot](https://github.com/gr1m0h/dot) — distributed by [TomeVault](https://tomevault.io).