webpack-mocha-plugin

Webpack plugin integration with mocha testing framework + coverage with istanbul.

Installation

    npm i -D webpack-mocha-plugin mocha istanbul remap-istanbul

Webpack Config

This webpack configuration will run your tests and write a html and json coverage report to coverage, after webpack compiles the project. If webpack is in watch mode tests are run after each compilation. You can configure entry and output how ever you like. The plugin will add all generated files ending in .js to the mocha test.

    const WebpackMochaPlugin = require('webpack-mocha-plugin');
    const nodeExternals = require('webpack-node-externals');
    
    module.exports = {
        target: 'node',
    
        entry: {
            test: __dirname + '/test.bundle.ts'
        },
    
        output: {
            path: '.tmp/test',
            filename: '[name].bundle.js'
        },
    
        resolve: {
            extensions: ['.ts', '.js']
        },
    
        externals: [nodeExternals()],
    
        devtool: 'inline-source-map',
    
        module: {
            rules: [
                {
                    enforce: 'pre',
                    test: /\.js$/,
                    loader: 'source-map'
                },
                {
                    test: /\.ts$/,
                    loader: 'awesome-typescript'
                },
                {
                    enforce: 'post',
                    test: /\.(js|ts)$/,
                    // Exlude tests so they don't show up in coverage report.
                    exclude: /\.(spec)\.(ts|js)$/,
                    loader: 'sourcemap-istanbul-instrumenter',
                    query: {
                        'force-sourcemap': true
                    }
                }
            ]
        },
    
        plugins: [
            new WebpackMochaPlugin({
                codeCoverage: true
            })
        ],
        // When using code coverage exclude the coverage report from being watched.
        // Otherwise you might get an infinite loop.
        watchOptions: {
            ignored: /coverage/
        }
    };

Options

    new WebpackMochaPlugin({
        mocha?: any = {};
        codeCoverage?: boolean = false;
        coverageVariable?: string = '__coverage__';
        coverageReports?: string[] = ['html', 'json'];
        coverageDir?: string = 'coverage';
    })

You can pass all options which the Mocha JS API takes in mocha. codeCoverage enables or disables generation of a report. coverageVariable is where the instrumenter puts the coverage information. coverageReports takes all reporters which istanbul can generate. coverageDir is the directory where the coverage report will be stored.

Test Bundle

    // This will only inlcude spec files and files required by them in the coverage report.
    // Tell webpack to bundle all spec files in a context.
    const ctx = require.context('src', true, /\.(spec)\.js/)
    
    // Evaluate all modules in context.
    ctx.keys().map(moduleId => ctx(moduleId))
    
    // This will include all files in the src directory so untest code shows up in the coverage
    // report.
    // Tell webpack to bundle all source files in a context.
    const ctx = require.context('src', true, /\.js/)
    
    // Evaluate all modules in context.
    ctx.keys().map(moduleId => ctx(moduleId))