karma-rollup

1.0.1 verified Mon Apr 27 auth: no javascript

Karma preprocessor that bundles ES2015 modules using Rollup for testing. Version 1.0.1 is the latest stable release (as of 2023+). Designed for use with Karma test runner, it integrates Rollup as a preprocessor to transpile and bundle ES module imports/exports into a single file per test file. Supports Rollup plugins (e.g., Bublé, Babel), custom preprocessors, watch mode with caching, and sourcemaps. Differentiators: lightweight compared to Webpack-based preprocessors, leverages Rollup's tree-shaking and fast bundling. Requires Rollup >=1.0.0 as a peer dependency.

Common errors

error Error: Cannot find module 'karma-rollup' ↓

cause karma-rollup is not installed or not listed in plugins.

fix

Run 'npm install karma-rollup --save-dev' and ensure plugins includes 'karma-*' or 'karma-rollup'.

error RollupError: You must supply output.name for IIFE format ↓

cause IIFE output format requires a name to avoid global scope collision.

fix

Add property 'output.name: 'MyProject'' to rollupPreprocessor.options.

error Error: No provider for "framework:jasmine"! (Resolving: framework:jasmine) ↓

cause Karma Jasmine framework not installed.

fix

Run 'npm install karma-jasmine --save-dev' and add 'jasmine' to frameworks array.

Warnings

gotcha 'input' property is handled automatically by karma-rollup; do not set it in rollupPreprocessor.options. ↓

fix Remove 'input' from options; the input file is determined by Karma's files and preprocessors.

gotcha Rollup 2.0+ changed the output format structure; older karma-rollup versions may not support Rollup >=2. Check peer dep: rollup >=1.0.0 (but may work with 2.x). ↓

fix Update karma-rollup or downgrade Rollup to >=1.0.0 <2.0.0; or test with Rollup 2.0 and adjust output config accordingly.

gotcha Using 'rollupPreprocessor' configuration, not 'rollup' – the key must be exactly 'rollupPreprocessor'. ↓

fix Set the config key as 'rollupPreprocessor' (not 'rollup') in karma.conf.js.

gotcha Missing 'name' in output for 'iife' format will cause Rollup error: 'You must supply output.name for IIFE format'. ↓

fix Add 'output.name: 'YourProject'' to rollupPreprocessor.options.

gotcha If not using default plugins array, ensure 'karma-rollup' is included in the plugins list (or 'karma-*'). ↓

fix Add 'karma-rollup' to config.plugins or use the wildcard pattern 'karma-*'.

Install

npm install karma-rollup

yarn add karma-rollup

pnpm add karma-rollup

Imports

rollupPreprocessor
wrong
```
const rollupPreprocessor = require('karma-rollup')
```
correct
```
// Configure in karma.conf.js – no import needed
```
This package is a Karma plugin, not a direct import. It's loaded via Karma's plugin system (plugins: ['karma-*']).
customPreprocessors
wrong
```
const customPreprocessors = require('karma-rollup').customPreprocessors
```
correct
```
// Configure in karma.conf.js – no import needed
```
Custom preprocessors are defined inside karma.conf.js per Karma documentation; not exported by this package.
karma-rollup
wrong
```
npm install karma-rollup
```
correct
```
npm install karma-rollup --save-dev
```
Always install as a dev dependency; it's only used during testing.

Quickstart

Basic Karma configuration using karma-rollup preprocessor with Rollup and Bublé for ES2015 transpilation, outputting in IIFE format with inline sourcemaps.

// karma.conf.js
module.exports = function(config) {
  config.set({
    basePath: '',
    frameworks: ['jasmine'],
    files: [
      'test/**/*.spec.js'
    ],
    plugins: [
      'karma-jasmine',
      'karma-chrome-launcher',
      'karma-rollup'
    ],
    preprocessors: {
      'test/**/*.spec.js': ['rollup']
    },
    rollupPreprocessor: {
      options: {
        plugins: [require('rollup-plugin-buble')()],
        output: {
          format: 'iife',
          name: 'MyProject',
          sourcemap: 'inline'
        }
      }
    },
    browsers: ['ChromeHeadless'],
    reporters: ['progress'],
    port: 9876,
    colors: true,
    logLevel: config.LOG_INFO,
    autoWatch: true,
    singleRun: false,
    concurrency: Infinity
  });
}