mockr

Mock API server for frontend prototyping. Declare a typed mockGroup() builder — it infers each handler's body, req.params, and ctx from one endpoint map — seed an in-memory store for full CRUD, and compose groups across files. Mock the routes you're building, proxy the rest to a real backend with ctx.forward(), or seed a store from the real backend once with .data(url, loader) and mutate it locally. zod body/query validation, per-endpoint scenarios, WebSocket endpoints, and a Chrome extension that records traffic and maps it to local files.

Docs: https://yoyo-67.github.io/mockr/

Install

npm install @yoyo-org/mockr zod

Add "type": "module" to package.json. Run with npx tsx mock.ts — no build step.

Quick example

import { mockr, mockGroup } from '@yoyo-org/mockr';
import { z } from 'zod';

type Todo = { id: number; title: string; done: boolean };
type Endpoints = {
  '/api/todos': Todo[];
  '/api/todos/:id': Todo;
};

const todos = mockGroup<Endpoints>()
  .data('/api/todos', [{ id: 1, title: 'Buy milk', done: false }])
  .post('/api/todos', {
    body: z.object({ title: z.string() }),
    fn: (req, ctx) => {
      ctx.endpoint('/api/todos').insert({ id: Date.now(), title: req.body.title, done: false });
      return ctx.endpoint('/api/todos').data;
    },
  })
  .patch('/api/todos/:id', {
    body: z.object({ done: z.boolean() }),
    fn: (req, ctx) => ctx.endpoint('/api/todos').update(Number(req.params.id), req.body),
  })
  .done();

await mockr({ port: 4000, groups: [todos] });

GET /api/todos returns the array, POST inserts, PATCH updates, DELETE removes — no glue code.

The old handler() / endpoints() functions are deprecated in favor of mockGroup() — see MIGRATION.md.

Where to next

• Concepts — the data-driven mental model
• Tutorial — eleven chapters, each a runnable example
• Reference — full API surface (handlers, WebSocket, recorder, CLI)
• Examples — copy-pasteable working servers

License

MIT