Istanbul Instrumenter Loader

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

Install

npm i -D istanbul-instrumenter-loader

Usage

`References`

`Structure`

├─ 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

// requires all tests in `project/test/src/components/**/index.js`
const tests = require.context('./src/components/', true, /index\.js$/);
 
tests.keys().forEach(tests);
 
// requires all components in `project/src/components/**/index.js`
const components = require.context('../src/components/', true, /index\.js$/);
 
components.keys().forEach(components);

ℹ️ 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$/,
          use: { loader: 'istanbul-instrumenter-loader' },
          include: path.resolve('src/components/')
        }
      ]
    }
    ...
  },
  reporters: [ 'progress', 'coverage-istanbul' ],
  coverageIstanbulReporter: {
    reports: [ 'text-summary' ],
    fixWebpackSourcePaths: true
  }
  ...
});

with `Babel`

You must run the instrumentation as a post step

webpack.config.js

{
  test: /\.js$|\.jsx$/,
  use: {
    loader: 'istanbul-instrumenter-loader',
    options: { esModules: true }
  },
  enforce: 'post',
  exclude: /node_modules|\.spec\.js$/,
}

Options

The loader supports all options supported by istanbul-lib-instrument

Name	Type	Default	Description
`debug`	`{Boolean}`	`false`	Turn on debugging mode
`compact`	`{Boolean}`	`true`	Generate compact code
`autoWrap`	`{Boolean}`	`false`	Set to `true` to allow return statements outside of functions
`esModules`	`{Boolean}`	`false`	Set to `true` to instrument ES2015 Modules
`coverageVariable`	`{String}`	`__coverage__`	Name of global coverage variable
`preserveComments`	`{Boolean}`	`false`	Preserve comments in `output`
`produceSourceMap`	`{Boolean}`	`false`	Set to `true` to produce a source map for the instrumented code
`sourceMapUrlCallback`	`{Function}`	`null`	A callback function that is called when a source map URL is found in the original code. This function is called with the source filename and the source map URL

webpack.config.js

{
  test: /\.js$/,
  use: {
    loader: 'istanbul-instrumenter-loader',
    options: {...options}
  }
}

Maintainers

Kir Belevich

npm