Jscov

Collect JavaScript code coverages. It works with istanbul.

Installation

Add this line to your application's Gemfile:

gem 'jscov'

And then execute:

$ bundle

Or install it yourself as:

$ gem install jscov

Usage

Install babel-plugin-istanbul.

$ yarn add -D babel-plugin-istanbul

And setup it. In babel.config.js:

module.exports = function (api) {
  // ....
  return {
    plugins: [
      // ...
      isTestEnv && 'babel-plugin-istanbul' // Add this
    ].filter(Boolean)
  }
}

Add Jscov middleware to rails middleware stack. Add the following in config/environments/test.rb:

[MyRailsApp]::Application.configure do |config|
  ...
  config.middleware.use Jscov::RackMiddleware
  ...
end

Load rspec helper. In spec/rails_helper.rb:

require 'jscov/rspec'

Configure selenium to capture the output of console.log:

RSpec.configure do |config|
  config.before(type: :system) do |example|
    caps = Selenium::WebDriver::Remote::Capabilities.chrome('chromeOptions' => { w3c: false }, 'goog:loggingPrefs' => { browser: 'ALL' })
    driven_by :selenium, using: :headless_chrome, options: { desired_capabilities: caps }
  end
end

Run NODE_ENV=test RAILS_ENV=test bin/rails assets:precompile for generating js codes that applied istanbul:

NODE_ENV=test RAILS_ENV=test bin/rails assets:precompile

OK, run rspec! It will dump collected coverage files in tmp/jscov. The collected coverages can be output as a report using nyc.

$ npx nyc report --temp-dir=tmp/jscov

Vue.js

To collect coverage for .vue files, you will need to change the configurations.

In babel.config.js:

module.exports = function (api) {
  // ....
  return {
    plugins: [
      // ...
      // Add below
      isTestEnv && [
        'babel-plugin-istanbul',
        {
          extension: ['.js', '.vue']
        }
      ]
    ].filter(Boolean)
  }
}

And, you need to add an argument to nyc:

$ npx nyc report --temp-dir=tmp/jscov --extension=.vue

Configuration

You can configure the following values.

Jscov.configure do |config|
  # config.coverage_report_dir_path = Rails.root.join("tmp/jscov")
end

License

The gem is available as open source under the terms of the MIT License.