The istanbul-instrumenter-loader from tarjei

istanbul-instrumenter-loader's Introduction

Istanbul instrumenter loader for webpack

Instrument JS files with istanbul-lib-instrument for subsequent code coverage reporting.

Install

npm install --save-dev istanbul-instrumenter-loader
# or
yarn add --dev istanbul-instrumenter-loader

Setup

References

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

testsContext.keys().forEach(testsContext);

// require all `project/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: {
            rules: [
                // instrument only testing sources with Istanbul
                {
                    test: /\.js$/,
                    include: path.resolve('src/components/'),
                    loader: 'istanbul-instrumenter-loader'
                }
            ]
        }
        …
    },
    reporters: [ 'progress', 'coverage-istanbul' ],
    coverageIstanbulReporter: {
        reports: [ 'text-summary' ],
        fixWebpackSourcePaths: true
    },
    …
});