我刚开始使用RSpec进行测试，不知道如何在测试创建新的Customer时修复此错误，其中我的CustomerController

class Api::V1::Customers::RegistrationsController < DeviseTokenAuth::RegistrationsController

  def create
        customer = Customer.new(email: params[:email],
                            password: params[:password],
                            password_confirmation: params[:password_confirmation],
                            first_name: params[:first_name],
                            last_name: params[:last_name],
                            telephone_number: params[:telephone_number],
                            mobile_phone_number: params[:mobile_phone_number])
        if customer.save
          customer.generate_verification_code
          customer.send_verification_code
          render json: {message: 'A verification code has been sent to your mobile. Please fill it in below.'}, status: :created
        else
          render json: customer.errors
        end
     end
  end
end

其中Customer中的generate_verification_code和send_verification_code

class Customer < ActiveRecord::Base

  def generate_verification_code
    self.verification_code = rand(0000..9999).to_s.rjust(4, "0")
    save
  end

  def send_verification_code
    client = Twilio::REST::Client.new
    client.messages.create(
      from: Rails.application.secrets.twilio_phone_number,
      to: customer.mobile_phone_number,
      body: "Your verification code is #{verification_code}"
    )
  end

end

和Customer的registrations_controller_spec.rb测试文件

require 'rails_helper'

RSpec.describe Api::V1::Customers::RegistrationsController, type: :controller do
    let(:customer) { FactoryBot.create(:customer) }

    before :each do
        request.env['devise.mapping'] = Devise.mappings[:api_v1_customer]
    end

    describe "Post#create" do
        it 'creates a new customer' do
            post :create, params: attributes_for(:customer)
            expect(response).to have_http_status(:created)
        end
    end
end

运行测试后，我收到以下错误：

Failure/Error:
   client.messages.create(
     from: Rails.application.secrets.twilio_phone_number,
     to: customer.mobile_phone_number
     body: "Your verification code is #{verification_code}"
   )

 Twilio::REST::RestError:
   Unable to create record: The requested resource /2010-04-01/Accounts//Messages.json was not found

我得到它，这个错误正在发生，因为在测试中它不应该调用外部API（当Twilio发送短信验证码号码）！
但有什么解决办法吗？