Decoupled dependency injection

acme_service_client.rb

class AcmeServiceClient
  def initialize(http_client, acme_response_translator)
    self.http_client = http_client
    self.acme_response_translator = acme_response_translator
  end

  def self.make(dependencies)
    instance = self.new(dependencies["http_client"], dependencies["acme_response_translator"])
    return instance
  end

  def self.create()
    real_http_client = HttpClient.new()
    real_acme_response_translator = AcmeResponseTranslator.new()
    instance = self.make({
      "http_client" => real_http_client,
      "acme_response_translator" => real_acme_response_translator
    })

    return instance
  end
end

acme_service_client.spec.rb

describe "AcmeServiceClient"
  beforeEach do
    mock_http_client = Mock::HttpClient.new()
    mock_acme_response_translator = Mock::AcmeResponseTranslator.new()

    client = AcmeServiceClient.make({
      "http_client" => mock_http_client,
      "acme_response_translator" => mock_acme_response_translator
    })
  end

  describe "Placing an order" do
    it "makes an HTTP POST request" do
      mock_http_client.should_receive(:post).with("/quantity/5")
      client.place_order({quantity: 5})
    end
  end
end

request-forwarder.js

var forwarder = function(listener, sender, logger){
  this.listener = listener;
  this.sender = sender;
  this.logger = logger;
}

forwarder.make = function(dependencies){
  dependencies.listener.on("request", function(data){
    dependencies.sender.send(data);
    dependencies.logger.log("A request was forwarded");
  });

  return new forwarder(dependencies.listener, dependencies.sender, dependencies.logger);
}

forwarder.create = function(){
  var listener = ZeroMqRequestListener.create();
  var sender = HttpRequestSender.create();
  var logger = FileLogger.create();

  return forwarder.make({
    listener: listener,
    sender: sender,
    logger: logger
  });
}

forwarder.prototype.close = function(){
  this.listener.close();
  this.sender.close();
  this.logger.log("The forwarder has closed");
  this.logger.close();
}