Karma on Rails

README.md

Use Karma.js with Ruby on Rails (Sprockets)

Inspired by http://monterail.com/blog/2014/karma-on-rails/

This basically allows you to reference your application JS files, which are generated by Sprockets, in the Karma config like this:

files: [
  '<%= require("application.js") %>',
  '<%= require("other.js") %>',
  'static/files/**/*.js'
]

Add PhantomJS gem to your Gemfile: gem "phantomjs"

Install Karma.js and the PhantomJS runner: npm install --save-dev karma karma-phantomjs-launcher

karma.conf.js.erb

// Karma configuration

module.exports = function(config) {
  config.set({

    // base path that will be used to resolve all patterns (eg. files, exclude)
    basePath: '<%= Rails.root %>',

    // list of files / patterns to load in the browser
    files: [
      '<%= require("application.js") %>',
      'spec/javascripts/**/*_spec.js'
    ],

    // start these browsers
    // available browser launchers: https://npmjs.org/browse/keyword/karma-launcher
    browsers: ['PhantomJS']

    // The rest of your config goes here
  });
};

karma.rake

require "karma_runner"

namespace :karma do
  task start: :environment do
    KarmaRunner.new.start
  end

  task run: :environment do
    exit KarmaRunner.new.start("--single-run")
  end
end

karma_runner.rb

require "erb"
require "phantomjs"

class KarmaRunner
  CONFIG_FILE = "karma.conf.js"

  def start(args = nil)
    @tempfiles = []
    Tempfile.open(CONFIG_FILE) do |f|
      f.write config_file
      f.flush
      env = { "PHANTOMJS_BIN" => Phantomjs.path }
      system(env, "$(npm bin)/karma start #{f.path} #{args}")
    end
  ensure
    @tempfiles.each do |file|
      file.close
      file.unlink
    end
  end

  def config_file
    template = Rails.root.join("spec", "#{CONFIG_FILE}.erb")
    ERB.new(template.read).result(binding)
  end

  def require(src)
    f = Tempfile.new(src)
    @tempfiles << f
    f.write Rails.application.assets.find_asset(src).to_s
    f.flush
    f.path
  end
end