Ruby on rails RSpec allow_的任何_实例在请求测试中不起作用

我是RSpec的新手，正在测试一些请求类型的webhook测试。 但在这里，即使我使用

允许任何
实例，它也会出错
得到500而不是200。我用binding.pry检查了每个变量，但看起来一切正常。
在我看来，模拟失败了，所以它返回
500
。
有什么想法吗

describe "stripe_invoice_created_webhook", type: :request do

  let(:card_invoice){ create(:card_invoice, id: invoice.id) }
  let(:invoice){ create(:invoice, payment_account_id: payment_card_account.payment_account_id) }
  let(:payment_card_account){ create(:payment_card_account,
                                     stripe_customer_id: event.data.object.customer) }
  let(:event){ StripeMock.mock_webhook_event('invoice.created', {
    closed: false
  }) }

  it 'responds 200 to invoice_created webhook with valid endpoint' do
    allow_any_instance_of(CardInvoice).to receive(:process_invoice_items)
    allow_any_instance_of(CardInvoice).to receive(:process!)

    post '/stripe-events', event.as_json
    expect(response.status).to eq 200
    expect{ card_invoice.process_invoice_items }.not_to raise_error
    expect{ card_invoice.process! }.not_to raise_error
  end

原始代码是

class InvoiceCreated
  def call(event)
    invoice = event.data.object

    # NOTE: Skip if the invoice is closed.
    if invoice.closed == false
      stripe_customer = invoice.customer
      payment_account = PaymentCardAccount.find_by(stripe_customer_id: stripe_customer)
      card_invoice = Invoice.find_card_invoice_in_this_month_within(payment_account: payment_account)

      card_invoice.process_invoice_items(stripe_customer: stripe_customer,
                                         event_invoice_id: invoice.id)
      card_invoice.process!(:pending, id: invoice.id)
    end
  end
end

是的，嘲笑失败了。您期望对象CardVoice接收进程！或处理发票项，但尚未指定返回值。allow_any_instance_的语法为

allow_any_instance_of(Object).to receive(:function).and_return(:return_value)

谢谢你的回答。但是，返回（true）不起作用。为什么呢？