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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

Name

Type

Default

Description

debug

{Boolean}

{Boolean} false Turn on debugging mode

Name

Type

Default

Description

compact

{Boolean}

{Boolean} true Generate compact code

Name

Type

Default

Description

autoWrap

{Boolean}

{Boolean} false Set to true to allow return statements outside of functions

Name

Type

Default

Description

esModules

{Boolean}

{Boolean} false Set to true to instrument ES2015 Modules

Name

Type

Default

Description

coverageVariable

{String}

{String} __coverage__ Name of global coverage variable

Name

Type

Default

Description

preserveComments

{Boolean}

{Boolean} false Preserve comments in output

Name

Type

Default

Description

produceSourceMap

{Boolean}

{Boolean} false Set to true to produce a source map for the instrumented code

Name

Type

Default

Description

sourceMapUrlCallback

{Function}

{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

Juho Vepsäläinen

Joshua Wiens

Michael Ciniawsky

Matt Lewis