AI agent skill for testing Zod schemas — Jest/Vitest patterns, mock data, property-based testing. Works with Claude Code, Cursor, Codex, Windsurf.

Zod Testing

Created by Anivar Aravind

An AI agent skill for testing Zod schemas with Jest and Vitest.

The Problem

AI agents often write schema tests that only check the happy path, use parse() instead of safeParse() (crashing instead of failing), test schema internals (.shape, ._def) instead of behavior, or hardcode mock data instead of generating it from the schema. The result: tests that miss regressions and break on harmless refactors.

This Solution

A focused testing skill covering schema correctness testing, error assertion patterns, mock data generation, snapshot testing with z.toJSONSchema(), property-based testing, structural testing, and drift detection — with 14 anti-patterns showing exactly what goes wrong and how to fix it.

Install

npx skills add anivar/zod-testing -g

Or with full URL:

npx skills add https://github.com/anivar/zod-testing

Baseline

• zod ^4.0.0
• Jest or Vitest
• TypeScript ^5.5

What's Inside

Testing Approaches

Anti-Patterns

14 common testing mistakes with BAD/GOOD code examples:

• Testing schema internals instead of behavior
• Not testing error paths (only happy path)
• Using parse() in tests (crashes instead of failing)
• Not testing boundary values (min/max edges)
• Hardcoding mock data i