order

order.rb

class Order
  attr_accessor :status

  def initialize(adapter = MyWhateverAdapter.new)
    @adapter = adapter
  end

  def pay!
    @response = @adapter.pay(self)
  end
   
  def paid?
    @response.status
  end
end

order_spec.rb

describe Order do
  context "A valid order" do
    let(:adapter) { double("An Adapter") }
    let(:response) { double("My Response") }

    describe "A successful transaction" do
      before do
        adapter.should_receive(:pay).with(order).and_return(response)
        response.should_receive(:status).and_return(true)
      end

      it "should be a paid order" do
        order = Order.new(MyWhateverAdapter.new)
        order.pay!
        order.should be_paid
      end
    end

    describe "An unsuccessful transaction" do
      before do
        adapter.should_receive(:pay).with(order).and_return(response)
        response.should_receive(:status).and_return(false)
      end

      it "should not be a paid order" do
        order = Order.new
        order.pay!
        order.should_not be_paid
      end
    end
  end
end