如何为我的函数编写rspec？

Question

def get_payment
        @payment   = current_merchant.payments.find_by_id(params[:id]) if params[:id].match(/^(\d)+$/)
        @payment ||= current_merchant.payments.find_by_reference(params[:id])

        raise ActiveRecord::RecordNotFound if @payment.nil?
        @payment
      end

我已经为上面的代码编写了rspec但是看起来不合理。我已经为上面的代码编写了rspec但似乎不合理 Params [：id]仅包含整数，params [：reference]包含两个数字

describe "GET show" do
    it "can find payment by id" do
      get :show, id: payment.id
      expect(response).to be_success
      expect(assigns(:payment)).to eq(payment)
    end

    it "can find payment by reference" do
      get :show, id: payment.reference
      expect(response).to be_success
      expect(assigns(:payment)).to eq(payment)
    end
  end