unplugin-ts-mock

A build-time bundler plugin that scans TypeScript types and auto-generates faker-based mock data.
Supports Vite, webpack, Rollup, and esbuild.

Demo

# Requires Node.js 20+
cd test-vite
npm install
npm run dev   # http://localhost:5173

Mock data generated by createMock<User>(), createMock<Post>(), etc. is displayed as cards.
Click Regenerate to produce new faker values.

Usage

Write createMock<T>() in your code — the plugin replaces it with an object literal at build time.
Type inference and autocomplete work as-is with zero runtime overhead.

Installation

npm install unplugin-ts-mock

Plugin setup

// vite.config.ts
import TsMock from 'unplugin-ts-mock/vite'

export default {
  plugins: [TsMock()]
}

// webpack.config.js
const TsMock = require('unplugin-ts-mock/webpack')

module.exports = {
  plugins: [TsMock()]
}

// rollup.config.js
import TsMock from 'unplugin-ts-mock/rollup'

export default {
  plugins: [TsMock()]
}

// esbuild
import TsMock from 'unplugin-ts-mock/esbuild'

await build({
  plugins: [TsMock()]
})

API

import { createMock, createMockList } from 'unplugin-ts-mock'
import type { User, Post } from './types'

const user  = createMock<User>()       // inferred as User
const post  = createMock<Post>()
const users = createMockList<User>(3)  // inferred as User[]

After build, the actual bundle contains:

const user = {
  id: "f3152fb1-...",
  name: "Lola Friesen",
  email: "[email protected]",
  role: Role.Admin,
  createdAt: "2024-01-15T09:23:00.000Z",
  ...
}

The createMock<T>() call is replaced entirely with an inlined object literal.

Options

TsMock({
  dir:     './src',        // directory to scan (default: project root)
  exclude: ['fixtures'],   // additional directory names to exclude
})

Supported types

| Feature | Support | |---|---| | interface, type alias, enum | ✓ | | union, intersection, tuple | ✓ | | Partial / Required / Readonly / Pick / Omit / Promise / Array<T> | ✓ | | interface extends inheritance | ✓ | | Auto-discovery of all project files | ✓ | | Types from node_modules | ✓ via TypeChecker | | Namespaced types (WebAssembly.Memory, etc.) | ✓ via TypeChecker | | Function types / method signatures | ✓ generates () => {} stub | | Circular references | ✓ auto-blocked (depth limit 6) | | Advanced utilities (Extract, Exclude, ReturnType, …) | △ generates {} |

Field name inference

Field names are matched to produce meaningful values.

| Pattern | Example fields | Generated value | |---|---|---| | Exact match | id | UUID | | Exact match | name, email, phone, company | faker equivalent | | Exact match | timezone, locale, slug, ip, mimeType | faker equivalent | | *Id suffix | userId, teamId | UUID | | *At suffix | createdAt, updatedAt | ISO date string | | *Date suffix | startDate, dueDate | ISO date string | | *Url suffix | avatarUrl, imageUrl | URL | | Other string | — | lorem ipsum word |

Caveats

Optional fields (?) are omitted ~30% of the time.
Results vary per run — override specific fields after generation if a fixed value is required.

Advanced utility types (Extract, Exclude, ReturnType, Parameters, etc.) generate {}.

How it works

Directory scan
  → collect .ts / .tsx files (test and story files excluded)
  → ts.createProgram()   build full program (auto-detects tsconfig.json)
  → TypeChecker          resolve TypeReferences in declaration context
  → faker                generate random data matching field types and names

[Plugin]
  → detect createMock<T>() patterns via regex
  → extract generic argument T and generate mock
  → replace call with inlined object literal
  → auto-inject missing enum imports