configus.rb

Configus.build Rails.env do               
                                          
  env :production do                      
                                          
    services do                           
      stripe "StripeService"              
      stripe_gateway "StripeGateway"      
    end                                   
                                          
  end                                     
                                          
  env :development, parent: :production do
                                          
  end                                     
                                          
  env :test, parent: :production do       
    services do                           
      stripe_gateway "StripeGatewayStub"  
    end                                   
  end                                     
                                          
end                                       

create_stripe_invoce_item_job.rb

class CreateStripeInvoceItemJob < Struct.new(:invoce_id)
  include BaseJob

  def perform
    ServiceLocator.service(:stripe).create_invoice_item(invoce_id)
  end

end

create_stripe_invoce_item_job_spec.rb

describe CreateStripeInvoceItemJob, "#perform" do

  it "calls StripeService.create_invoce_item" do
    invoce_id = 123

    service_mock = mock("StripeService")
    service_mock.should_receive(:create_invoice_item).with(invoce_id)

    ServiceLocator.set_service(stripe: service_mock) do
      CreateStripeInvoceItemJob.new(invoce_id).perform
    end

  end

end

service_locator.rb

class ServiceLocator

  class << self

    def set_service(hash, &block)
      prev = {}
      hash.symbolize_keys.each do |name, srv|
        prev[name] = services[name]
        services[name]= srv
      end
      if block_given?
        begin
          block.call
        ensure
          set_service(prev)
        end
      end
    end

    def service(name)
      sname = name.to_sym
      services[sname] ||= configus.services.send(sname).constantize
    end

    private

    def services
      @services ||= {}
    end

  end

end