Introduction

Test fixtures and offline mock data drift from the real shape over time. A field is renamed in the schema, the fixture is not, and nothing fails until a real request breaks.

shamock closes that gap with two tools:

• Validation. Check any mock value against the same Standard Schema validator (Zod, Valibot, ArkType…) your app uses. A stale fixture fails loudly.
• Mock API. Serve seed data from an in-process REST API that answers fetch calls. No server needed.

shamock needs only a { schema } object, not an SDK resource type. It has zero dependencies and requires Node.js 22 or later.

Install

pnpm add shamock

A minimal example

import { parseMock } from 'shamock'
import { z } from 'zod'

const user = { schema: z.object({ id: z.number(), name: z.string() }) }

await parseMock(user, { id: 1, name: 'Alice' })

It throws MockValidationError when the value does not match the schema.

From here:

• Mock API: serve seed data over fetch.
• Pairing with nexdk: use shamock next to a nexdk SDK.
• shamock API: every runtime export.