Installation

Add this line to your application's Gemfile:

gem 'propshaft-js-coverage'

Add the compiler to propshaft

# config/initializers/assets.rb

if ENV["COVERAGE"]
  Propshaft::Js::Coverage::Compiler.configure do |config|
    config.should_process = ->(path) {
      return false if path.match?(/vendor\/assets\//)
      return false if path.match?(/gems\//)
      return true
    }
  end

  Rails.application.config.assets.compilers << [
    "text/javascript", Propshaft::Js::Coverage::Compiler
  ]
end

Get the coverage reports after running your tests

# test/application_system_test_case.rb

require "test_helper"

class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
def teardown
    __coverage__ = page.evaluate_script <<-JS
        JSON.stringify((typeof __coverage__ !== 'undefined') ? __coverage__ : null)
    JS

    if __coverage__ != "null"
      File.write("#{JS_COVERAGE_DIR}/#{Time.now.to_i.to_s}.json", __coverage__)
    end

    super
  end
end

Convert to lcov and generate html report

nyc report --reporter=lcov --temp-dir tmp/js-coverage --report-dir tmp/js-coverage
genhtml -q -o ./coverage ./tmp/js-coverage/lcov.info ./coverage/lcov/simplecov.lcov

How it works

This gem uses istanbul instrumenter to add coverage to your javascript files. It will add a global variable __coverage__ to your javascript files. You can then use this variable to get the coverage report.

Configuration

TBD

Contributing

Clone the repo and run bundle install to install the dependencies.

Prepare the js script by running yarn install and yarn run build in the js/instrumenter directory.

Release

Run ./scripts/release.sh to release a new version after updating the version in lib/propshaft/js/coverage/version.rb.