dependency_injection.rb

# lib/services/user/signup_service.rb

module Services
  module User
    class SignUpService
      attr_reader :publish_statistics_service,
                  :send_email_confirmation_service

      def initialize(
        user_publish_statistics_service:,
        user_send_email_confirmation_service:, 
      )
        @publish_statistics_service = user_publish_statistics_service
        @send_email_confirmation_service = user_send_email_confirmation_service
      end

      def call(user)
        user.signed_up_at = Time.now
        user.save!

        publish_user_statistics_service.call(user, 'signup')
        send_user_email_confirmation_service.call(user)
      end
    end
  end
end

# spec/services/user/signup_service_spec.rb

require 'spec_helper'

RSpec.describe Services::User::SignupService do
  let(:publish_stat_service) { double('publish_stats', call: nil) }
  let(:send_email_service) { double('send_email', call: nil) }
  
  let(:service) do
    described_class.new(
      user_publish_statistics_service: publish_stat_service,
      user_send_email_confirmation_service: send_email_service
    )
  end
  
  describe '.call' do
    let(:user) { FactoryGirl.build(:user) }
    
    before do
      allow(user).to receive(:save!)
    end
    
    it 'sets signed up time' do
      expect {
        service.call(user)
      }.to change(user, :signed_up_at).from(nil)
    end
    
    it 'saves user' do
      expect(user).to receive(:save!).once
      
      service.call(user)
    end
    
    # No need to test that publish stat service is sending stats
    # it will be tested in it's own spec file
    it 'publishes statistics' do
      expect(publish_stat_service).to receive(:call).with(user, 'signup')
      
      service.call(user)
    end
    
    # No need to test that send email service is sending email
    # it will be tested in it's own spec file
    it 'sends confirmation email' do
      expect(send_email_service).to receive(:call).with(user)
      
      service.call(user)
    end
  end
end