MockIt

MockIt is a REST API mocking library for JavaScript and TypeScript.

It supports three runtime patterns:

• MockServer: run a real mock API on a local port
• HttpInterceptor: intercept outbound HTTP in the current Node process
• RemoteMockServer: change a running MockServer from tests or scripts

| Feature | Use case | | --- | --- | | MockServer | Run a real mock API server for frontend development, browser automation, or any other process that needs a URL to call. | | HttpInterceptor | Intercept fetch, http, https, and Axios inside the current Node process without starting a server. | | RemoteMockServer | Update a running standalone mock from Playwright, API tests, or external scripts. | | TypeScript defaults | Load reusable default mocks from a typed config file. | | OpenAPI / Swagger loading | Generate mock endpoints and sample responses from an API spec. | | Request matching | Match by method, headers, cookies, query, bearer token, and body. | | Response control | Return delays, templates, faults, sequences, and limited-use responses. | | Dashboard and admin APIs | Inspect mocks, requests, unmatched calls, and pending expectations. |

Live docs: https://toolstackhq.github.io/mockit/

Install:

npm install @toolstackhq/mockit

Choose A Runtime

Use MockServer when:

• a browser, UI, or another process must call a real HTTP endpoint
• you want a mock to stay running outside a test process
• manual testers or QA automation need a stable fake backend

Use HttpInterceptor when:

• the code under test already runs in Node
• you want to fake outbound HTTP without starting a server
• your Node code uses fetch, Axios, http, or https

Use RemoteMockServer when:

• MockServer is already running
• the test should change mock behavior without starting the server itself

Quick Start

Create a TypeScript config:

npx @toolstackhq/mockit init

In a terminal, init can either:

• write the default starter config
• ask a few questions and generate endpoints for you

Start a standalone mock:

npx @toolstackhq/mockit serve --config ./mockit.config.ts --port 3001

The dashboard is available at:

http://127.0.0.1:3001/_mockit

TypeScript Config Example

import { defineConfig } from '@toolstackhq/mockit';

export default defineConfig([
  {
    path: '/api/balance',
    method: 'GET',
    response: {
      status: 200,
      body: { balance: 200, currency: 'AUD' },
    },
  },
]);

In-Process Interceptor Example

Use HttpInterceptor when your code already runs in Node and you do not want to start a mock server.

import axios from 'axios';
import { HttpInterceptor } from '@toolstackhq/mockit';

const interceptor = new HttpInterceptor({ onUnhandled: 'fail' });

interceptor.expect('/api/users')
  .method('GET')
  .returns(200)
  .withBody([{ id: 1, name: 'Jane Doe' }]);

interceptor.enable();

const response = await axios.get('https://api.example.com/api/users');
console.log(response.data);

interceptor.disable();

The request still looks like a real outbound HTTP call, but MockIt returns the response inside the same Node process.

npm Script

{
  "scripts": {
    "mockit": "mockit serve --config ./mockit.config.ts --port 3001"
  }
}