rollup-plugin-mock-imports

1.0.8 verified Mon Apr 27 auth: no javascript maintenance

Rollup plugin (v1.0.8) for mocking ESM imports during bundling, using `__mocks__` directories (like Jest) or a custom `node_mockdules` folder. Designed for pre-compilation testing scenarios (e.g., Svelte components with JSDOM), it intercepts resolved module IDs before other Rollup plugins. Configuration options include `mockall`, `ignore`, and `mock` patterns. Requires Rollup ^0.66.6 as peer dependency. Ships TypeScript types. Release cadence: low (last updated 2019).

Common errors

error Error: Cannot find module 'rollup' ↓

cause Rollup is a peer dependency and not installed automatically

fix

npm install --save-dev rollup@^0.66.6

error 'mockImports' is not exported from 'rollup-plugin-mock-imports' ↓

cause Default import used instead of named import

fix

Use import { mockImports } from 'rollup-plugin-mock-imports';

Warnings

breaking Rollup peer dependency is ^0.66.6 – may not work with Rollup >=1.0.0 ↓

fix Use Rollup ^0.66.6 or test compatibility with newer versions; consider forking or updating if needed.

gotcha mockImports must come before other module resolution plugins (e.g., rollup-plugin-node-resolve) or mocks may be skipped ↓

fix Place mockImports() first in the plugins array.

gotcha Mock imports only work for static ES imports; dynamic import() or CommonJS require() are not mocked ↓

fix Ensure imports are static ESM statements; convert dynamic imports to static or use alternative mocking.

gotcha Plugin creates a virtual node_mockdules folder alongside node_modules – name is critical and non-standard ↓

fix Do not rename the folder; the path is hardcoded relative to node_modules. For custom paths, use nodePath option.

Install

npm install rollup-plugin-mock-imports

yarn add rollup-plugin-mock-imports

pnpm add rollup-plugin-mock-imports

Imports

mockImports
wrong
```
import mockImports from 'rollup-plugin-mock-imports'
```
correct
```
import { mockImports } from 'rollup-plugin-mock-imports'
```
Named export, not default. CommonJS require: const { mockImports } = require('rollup-plugin-mock-imports')

Quickstart

Shows basic Rollup config with mockImports placed before other plugins, enabling global mocking with exceptions.

// rollup.config.js
import { mockImports } from 'rollup-plugin-mock-imports';
import resolve from 'rollup-plugin-node-resolve';
import commonjs from 'rollup-plugin-commonjs';

export default {
  input: 'src/main.js',
  plugins: [
    mockImports({ mockall: true, ignore: ['fs', 'path'] }),
    resolve(),
    commonjs()
  ],
  output: { file: 'dist/bundle.js', format: 'esm' }
};