istanbul-instrumenter-loader

What is istanbul-instrumenter-loader?

The 'istanbul-instrumenter-loader' is a webpack loader that instruments JavaScript files with Istanbul coverage, which is useful for generating code coverage reports for your tests.

What are istanbul-instrumenter-loader's main functionalities?

Instrumenting JavaScript files

This feature allows you to instrument JavaScript files for code coverage. The code sample shows how to configure webpack to use 'istanbul-instrumenter-loader' for all JavaScript files in the 'src/' directory.

module.exports = {
  module: {
    rules: [
      {
        test: /\.js$/,
        include: path.resolve('src/'),
        loader: 'istanbul-instrumenter-loader',
        options: { esModules: true }
      }
    ]
  }
};

Using with Babel

This feature demonstrates how to use 'istanbul-instrumenter-loader' in conjunction with 'babel-loader' to transpile and instrument JavaScript files. The code sample shows the configuration for webpack to use both loaders.

module.exports = {
  module: {
    rules: [
      {
        test: /\.js$/,
        include: path.resolve('src/'),
        use: [
          'babel-loader',
          {
            loader: 'istanbul-instrumenter-loader',
            options: { esModules: true }
          }
        ]
      }
    ]
  }
};

Other packages similar to istanbul-instrumenter-loader

babel-plugin-istanbul

The 'babel-plugin-istanbul' is a Babel plugin that instruments your code with Istanbul coverage. It is similar to 'istanbul-instrumenter-loader' but is used as a Babel plugin instead of a webpack loader. This can be more convenient if you are already using Babel for transpilation.

nyc

The 'nyc' package is a command-line interface for Istanbul. It provides a more comprehensive solution for code coverage, including running tests and generating reports. Unlike 'istanbul-instrumenter-loader', which is a webpack loader, 'nyc' can be used independently of webpack.

README

Istanbul instrumenter loader for webpack

Instrument JS files with Istanbul for subsequent code coverage reporting.
"Forked" from unfold/istanbul-instrument-loader.

Install

$ npm i -D istanbul-instrumenter-loader

Usage

Useful to get work together karma-webpack and karma-coverage. For example:

1. karma-webpack config
2. karma-coverage config
3. replace karma-coverage's code instrumenting with istanbul-instrumenter-loader's one:

config.set({
    ...
    files: [
      // 'src/**/*.js', << you don't need this anymore
      'test/**/*.js'
    ],
    ...
    preprocessors: {
        // 'src/**/*.js': ['coverage'], << and this too
        'test/**/*.js': [ 'webpack' ]
    },
    reporters: [ 'progress', 'coverage' ],
    coverageReporter: {
        type: 'html',
        dir: 'coverage/'
    },
    ...
    webpack: {
        ...
        module: {
            loaders: [ ... ],
            postLoaders: [ { // << add subject as webpack's postloader
                test: /\.js$/,
                exclude: /(test|node_modules|bower_components)\//,
                loader: 'istanbul-instrumenter'
            } ]
        },
        ...
    }
});

Documentation: Using loaders.

License

WTFPL