karma-webpack-with-fast-source-maps

1.10.2 verified Sat Apr 25 auth: no javascript maintenance

A fork of karma-webpack that adds support for file-based source maps and hot testing. Version 1.10.2 supports webpack 1-3. It allows running only affected tests on file changes using a manifest array, and provides faster source map generation via 'cheap-module-source-map' devtool. This package is largely superseded by modern karma-webpack versions (5+) that include better source map support and webpack 5 compatibility. It is not actively maintained and should not be used for new projects.

Common errors

error Module not found: Error: Can't resolve 'karma-webpack-with-fast-source-maps' ↓

cause Package not installed or misspelled in npm install.

fix

Run: npm install --save-dev karma-webpack-with-fast-source-maps

error Error: Cannot find module 'webpack' ↓

cause Missing peer dependency webpack.

fix

Run: npm install --save-dev webpack@3 (or compatible version)

error TypeError: Cannot read property 'webpack' of undefined ↓

cause Missing webpack configuration in Karma config.

fix

Add webpack: { ... } to karma.conf.js

error Error: 'preprocessors' should be an object ↓

cause Misplaced preprocessors or incorrect format in karma.conf.js

fix

Ensure preprocessors is a top-level config key with object value: preprocessors: { 'test.js': ['webpack'] }

Warnings

deprecated Package is deprecated; use karma-webpack v5+ for webpack 4/5 support. ↓

fix Replace with 'karma-webpack' and update configuration for version 5.

breaking Incompatible with webpack 4 and 5. Only supports webpack 1-3. ↓

fix Upgrade to karma-webpack v4+ for webpack 4 support, or v5+ for webpack 5.

gotcha Preprocessor name is 'webpack' not the package name. ↓

fix Use 'webpack' as preprocessor name, e.g., preprocessors: { 'test.js': ['webpack'] }.

gotcha The __karmaWebpackManifest__ variable is required in test entry file for selective test running; missing it may cause unexpected behavior. ↓

fix Ensure test entry file declares var __karmaWebpackManifest__ = []; before using it.

breaking No support for ES modules (ESM) natively; requires Babel or other transpilation. ↓

fix Add babel-loader or similar to webpack config to transpile ES modules.

Install

npm install karma-webpack-with-fast-source-maps

yarn add karma-webpack-with-fast-source-maps

pnpm add karma-webpack-with-fast-source-maps

Imports

plugin

wrong

plugins: ['karma-webpack-with-fast-source-maps']

correct

// In karma.conf.js, set frameworks: ['karma-webpack-with-fast-source-maps'] is not needed; just specify preprocessor

This package is a preprocessor plugin, not a framework. Do not register it as a framework or plugin.

preprocessor

wrong

preprocessors: { 'test/**/*.js': ['karma-webpack-with-fast-source-maps'] }

correct

preprocessors: { 'test/**/*.js': ['webpack'] }

The preprocessor name is 'webpack', not the full package name.

webpackOptions
wrong
```
webpack: { devtool: 'source-map' }
```
correct
```
webpack: { devtool: 'cheap-module-source-map', ... }
```
Using 'source-map' gives slower inline maps, 'cheap-module-source-map' is recommended for speed.

Quickstart

Karma configuration using karma-webpack-with-fast-source-maps with webpack preprocessor, fast source maps, and a single test entry point.

// karma.conf.js
module.exports = function(config) {
  config.set({
    browsers: ['ChromeHeadless'],
    frameworks: ['jasmine'],
    files: ['test/test_index.js'],
    preprocessors: {
      'test/test_index.js': ['webpack']
    },
    webpack: {
      devtool: 'cheap-module-source-map',
      module: {
        rules: [
          { test: /\.js$/, exclude: /node_modules/, use: 'babel-loader' }
        ]
      }
    },
    webpackMiddleware: { noInfo: true },
    singleRun: true
  });
};