How do i write a test case using rspec for private method

Hello I,m new to rails

I am writing test cases for using rspec gem

In my controller I have edit function. I have before action for edit function
This is my controller

before_action :authorize_user, only: %i[edit update destroy]
def edit
end

**private**

  def authorize_user
    id = Question.find(params[:id]).user_id
    redirect_to root_path if id != current_user.id
  end

This is my rspec/requests/question_rspec.rb

  describe "GET /edit" do
    before do
      sign_in(create(:user)) # Factory Bot user
    end
    it "render a successful response" do
      question = create(:question) #Factory bot question
      # question.user = current_user
      question.save
      get edit_question_url(question)
      expect(response).to be_successful
    end

  end

I'm getting an error like

Failure/Error: expect(response).to be_successful
       expected `#<ActionDispatch::TestResponse:0x00005652448f4c50 @mon_data=#<Monitor:0x00005652448f4c00>, @mon_data_..., @method=nil, @request_method=nil, @remote_ip=nil, @original_fullpath=nil, @fullpath=nil, @ip=nil>>.successful?` to be truthy, got false
     # ./spec/requests/questions_spec.rb:105:in `block (3 levels) in <main>'

Could anyone please let me know

All the resources that you mention, but the proper "theoretical" https://testmyspeed.onl/ way to do it would be to test that @client receives add_message_callback, and then indirectly test your private methods with integration tests.