babel-plugin-coverage

Note

This is a fork of babel-plugin-coverage by @dtinth, who did most of the work. This fork has a few changes on top of it:

1. Supports istanbul-style ignore hints, aka /* istanbul ignore next */.

2. Does not treat parts of conditionals and logical expressions as statements, which is an opinionated choice by babel-plugin-__coverage__. The behavior of this plugin is more akin to istanbul's original behavior.

Original README Below

A Babel plugin that instruments your code with __coverage__ variable. The resulting __coverage__ object is compatible with Istanbul, which means it can instantly be used with karma-coverage and mocha on Node.js (through nyc).

Note: This plugin does not generate any report or save any data to any file; it only adds instrumenting code to your JavaScript source code. To integrate with testing tools, please see the Integrations section.

Usage

Install it:

npm install --save-dev babel-plugin-__coverage__

Add it to .babelrc in test mode:

{
  "env": {
    "test": {
      "plugins": [ "__coverage__" ]
    }
  }
}

Integrations

karma

It just works with Karma. First, make sure that the code is already transpiled by Babel (either using karma-babel-preprocessor, karma-webpack, or karma-browserify). Then, simply set up karma-coverage according to the docs, but don’t add the coverage preprocessor. This plugin has already instrumented your code, and Karma should pick it up automatically.

It has been tested with bemusic/bemuse project, which contains ~2400 statements.

mocha on node.js (through nyc)

Configure Mocha to transpile JavaScript code using Babel, then you can run your tests with nyc, which will collect all the coverage report. You need to configure NYC not to instrument your code by setting this in your package.json:

  "nyc": {
    "include": [ "/" ]
  },

Ignoring files

You don't want to cover your test files as this will skew your coverage results. You can configure this by configuring the plugin like so:

"plugins": [ [ "__coverage__", { "ignore": "test/" } ] ]

Where ignore is a glob pattern.

Alternatively, you can specify only which will take precedence over ignore:

"plugins": [ [ "__coverage__", { "only": "src/" } ] ]