order_spec.rb

describe Order do
 let(:product){stub(:product)}
 let(:payment_gateway){stub(:payment_gateway)}
 let(:order){Order.new(payment_gateway)}

 it "confirm the order if the client has funds" do
  product.stub(:price).and_return(50)
  payment_gateway.stub(:user_has_funds).with(50).and_return(true)
  order.buy(product).should be_true
 end

end

sqmc_order_spec.rb

describe Order do
  let(:product){stub(:product)}
  let(:payment_gateway){mock(:payment_gateway)}
  let(:order){Order.new(payment_gateway)}

  it "the payment gateway is called with the order price" do
    product.stub(:price).and_return(50)
    payment_gateway.should_receive(:user_has_funds).with(50)
    order.buy(product)
  end

  it "confirm the order if the client has funds" do
    payment_gateway.stub(:user_has_funds).and_return(true)
    order.buy(product).should be_true
  end
end