Istanbul instrumenter loader for webpack

Instrument JS files with Istanbul for subsequent code coverage reporting.

Using Babel to transpile ES6/ES7? Use isparta-loader to coverage your original code.

Install

$ npm i -D istanbul-instrumenter-loader

Setup

References

• Using loaders
• karma-webpack
• karma-coverage

Project structure

Let's say you have the following:

├── src/
│   └── components/
│       ├── bar/
│       │   └── index.js
│       └── foo/
│           └── index.js
└── test/
    └── src/
        └── components/
            └── foo/
                └── index.js

To create a code coverage report for all components (even for those for which you have no tests yet) you have to require all the 1) sources and 2) tests. Something like it's described in "alternative usage" of karma-webpack:

test/index.js

// require all `test/components/**/index.js`
const testsContext = require.context('./src/components/', true, /index\.js$/);

testsContext.keys().forEach(testsContext);

// require all `src/components/**/index.js`
const componentsContext = require.context('../src/components/', true, /index\.js$/);

componentsContext.keys().forEach(componentsContext);

This file will be the only entry point for Karma:

karma.conf.js

config.set({
    …
    files: [
        'test/index.js'
    ],
    preprocessors: {
        'test/index.js': 'webpack'
    },
    webpack: {
        …
        module: {
            preLoaders: [
                // instrument only testing sources with Istanbul
                {
                    test: /\.js$/,
                    include: path.resolve('src/components/'),
                    loader: 'istanbul-instrumenter'
                }
            ]
        }
        …
    },
    reporters: [ 'progress', 'coverage' ],
    coverageReporter: {
        type: 'text'
    },
    …
});

License

WTFPL