isparta instrumenter loader for webpack

Instrument Babel code with isparta for subsequent code coverage reporting.

Install

$ npm i -D isparta-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

var babelPresets = ['es2015', 'stage-0', 'react'];

config.set({
    …
    files: [
        'test/index.js'
    ],
    preprocessors: {
        'test/index.js': 'webpack'
    },
    webpack: {
        …
        module: {
            preLoaders: [
                // transpile all files except testing sources with babel as usual
                {
                    test: /\.js$/,
                    exclude: [
                        path.resolve('src/components/'),
                        path.resolve('node_modules/')
                    ],
                    loader: 'babel',
                    query: babelPresets
                },
                // transpile and instrument only testing sources with isparta
                {
                    test: /\.js$/,
                    include: path.resolve('src/components/'),
                    loader: 'isparta',
                    // *optional* isparta options: istanbul behind isparta will use it
                    query: {
                        embedSource: true,
                        noAutoWrap: true,
                        // these babel options will be passed only to isparta and not to babel-loader
                        babel: {
                            presets: babelPresets
                        }
                    }
                }
            ]
        }
        …
    },
    reporters: [ 'progress', 'coverage' ],
    coverageReporter: {
        type: 'text'
    },
    …
});

License

WTFPL