Configuring a Rake Task for karma and jasmine

karma.rake

require 'open3'

namespace :karma do

  task :start => :environment do
    with_tmp_config :start
  end

  task :run => :environment do
    with_tmp_config :start "--single-run"
  end

  private

  def with_tmp_config(command, args=nil)
    Tempfile.open(['karma_unit', '.js'], Rails.root.join('tmp')) do |f|
      f.write unit_js(application_spec_files)
      f.flush

      puts "Running karma with configuration file: #{f.path}"
      puts 'Open Chrome -> localhost:9676/debug.html'

      Open3.popen2e("karma start #{f.path} #{args}") do |stdin, stdout_and_stderr, wait_thr|
        puts stdout_and_stderr.gets(nil)
        raise "Karma tests failed" unless wait_thr.value.success?
      end
    end
  end  

  def application_spec_files
    Rails.application.assets.find_asset("application_spec.js").to_a.map {|e| e.pathname.to_s } 
  end

  def unit_js(files)
    unit_js = File.open('spec/javascripts/karma.unit.js', 'r').read
    unit_js.gsub "APPLICATION_SPEC", "\"#{files.join("\",\n\"")}\""
  end

end

karma.unit.js

// Karma configuration
// Generated on Thu Nov 13 2014 18:24:05 GMT+0200 (EET)

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

    // base path that will be used to resolve all patterns (eg. files, exclude)
    basePath: '..',


    // frameworks to use
    // available frameworks: https://npmjs.org/browse/keyword/karma-adapter
    frameworks: ['jasmine'],


    // list of files / patterns to load in the browser
    files: [
      APPLICATION_SPEC,
      'spec/javascripts/**/*_spec.coffee'
    ],


    // list of files to exclude
    exclude: [
      '**/*.erb'
    ],


    // preprocess matching files before serving them to the browser
    // available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
    preprocessors: {
      '**/*.coffee': ['coffee']
    },


    // test results reporter to use
    // possible values: 'dots', 'progress'
    // available reporters: https://npmjs.org/browse/keyword/karma-reporter
    reporters: ['progress'],


    // web server port
    port: 9876,


    // enable / disable colors in the output (reporters and logs)
    colors: true,


    // level of logging
    // possible values: config.LOG_DISABLE || config.LOG_ERROR || config.LOG_WARN || config.LOG_INFO || config.LOG_DEBUG
    logLevel: config.LOG_INFO,


    // enable / disable watching file and executing tests whenever any file changes
    autoWatch: true,


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


    // Continuous Integration mode
    // if true, Karma captures browsers, runs the tests and exits
    singleRun: false
  });
};