Rspec正在调用原始方法而不是模拟

Question

我对rspec有一个问题，即在方法中创建一个外部对象，而不是使用该对象的模拟，创建实际对象。

Ruby代码：

module A
  class B
    def initialize
      @my_variable = function_call
    end

    private

    def function_call
      external_object = ExternalObject.new(123)
      {
        key1: external_object.external_method.to_s,
        key2: external_object.to_s
      }
    end
  end
end

Rspec的：

describe A:B do

  let(:mock_external_obj) { 'mock_ext_obj' }
  let(:mock_external_obj_to_s) { 'mock_ext_obj_to_str' }

  before do
    allow(ExternalObject).to receive(:new).and_return(mock_external_obj)
    allow(mock_external_obj).to receive(:to_string).and_return(mock_external_obj_to_s)
    allow(mock_external_obj).to receive(:external_method).and_return(my_variable)
  end

  subject { described_class.new }

  context 'does something' do
    it 'does something else' do
      expect(subject.my_variable).to eq({
                                         key1: mock_external_obj_to_s,
                                         key2: mock_external_obj_to_s
                                       })
    end
  end
end

在上面的示例中，我希望ExternalObject.new(123)返回mock_external_obj。相反，它实际上是调用ExternalObject.new(123)和external_object.external_method.to_s来调用实际的外部对象的方法。