问Rspec，如何使用多个服务调用测试方法？

EN

class Service1
  def self.foo
    new.foo
  end

  def foo
    puts 'foo'
  end
end

class Service2
  def bar
    3.times.each do 
      Service1.foo
    end
  end
end

describe "#bar" do
  let(:service1) { class_double("Service1") }

  it "calls Service1.foo three times" do
    expect(service1).to receive(:foo).exactly(3).times

    Service2.bar
  end
end

class Service1
  def foo
    puts 'foo'
  end
end

class Service2
  def bar
    3.times.each do 
      Service1.new().foo
    end
  end
end

let(:mocked_service) { instance_spy Service1 }

it "calls Service1.foo three times" do
  allow(Service1).to receive(:new).and_return mocked_service

  Service2.bar

  expect(mocked_service).to have_received(:foo).exactly(3).times
end