How to use helper methods in RSpec?

I have a helper method defined in my RSpec spec which creates an instance of the class Dog. But the spec is not able to recognize the method call dog.good_dog.

helpers_demo_spec.rb

class Dog

    attr_reader :good_dog, :has_been_walked 

    def initialize(good_or_not)
        @good_dog = good_or_not 
        @has_been_walked = false 
    end 

    def walk_dog 
        @has_been_walked = true 
    end 

end 


describe Dog do 

    # helper method 
    def create_and_walk_dog(good_or_bad)
        Dog.new(good_or_bad).walk_dog 
    end 

    it 'should be able to create and walk a good dog' do
        dog = create_and_walk_dog(true)
        expect(dog.good_dog).to be true
        expect(dog.has_been_walked).to be true 
    end 

end

Error Log:

C:\nital\my-data\my-sample-apps\Rails-Samples\rspec-samples\lib>rspec spec\helpers_demo_spec.rb
F

Failures:

  1) Dog should be able to create and walk a good dog
     Failure/Error: expect(dog.good_dog).to be true

     NoMethodError:
       undefined method `good_dog' for true:TrueClass
     # ./spec/helpers_demo_spec.rb:26:in `block (2 levels) in <top (required)>'

Finished in 0.001 seconds (files took 0.33463 seconds to load)
1 example, 1 failure

Failed examples:

rspec ./spec/helpers_demo_spec.rb:24 # Dog should be able to create and walk a good dog