Rspec return No route matches when using scoped route

I have a route that is defined as this in my routes.rb as so

scope ':prefix', as: :foo, controller: 'foo_paths', action: :placeholder do
  get 'foo/:id', as: 'result'
end

The issue is when running my test it always returns

 Failure/Error: subject { get :placeholder }

 ActionController::UrlGenerationError:
   No route matches {:action=>"placeholder", :controller=>"foo_paths"}

Here's all my code I can't find any error everything works fine in the browser and rake routes return the expected route.

foo_paths_controller.rb

class FooPathsController < ApplicationController
  def placeholder
    render nothing: true, status: :service_unavailable
  end
end

foo_paths_controller_spec.rb

describe FooPathsController, type: :controller do
  describe "GET 'placeholder'" do
    subject { get :placeholder }

    it 'renders an empty page with service unavailable http error' do
      subject

      it { expect(subject).to have_http_status(503) }
      it { expect(subject.body).to be_blank }
    end
  end
end

rake routes

foo_result GET      /:prefix/foo/:id(.:format)                                                            foo_paths#placeholder