fun.rb

class Questionnaire < ApplicationRecord
  has_many :questions
  has_many :member_questionnaires
  has_many :users, through: :member_questionnaires
  accepts_nested_attributes_for :question

end

class Question < ApplicationRecord
  belongs_to :questionnaire
  has_one :answer
end

class Answer < ApplicationRecord
  belongs_to :question
end



%h1
  questionnaires#show

= form_for @questionnaire do |f|
  = @questionnaire.questions.each do |question|
    %h1
      = question.description
    - fields_for :question, question.create_answer do |answer|
      = answer.text_field :description


#what im trying to do... iterate over the questions and then have a text_field for the answers
# show the question.description and below that show a answer text_field ( the user cannot edit questions )


  resources :questionnaires, only: [:index, :edit, :update] do
    resources :questions, only: [] do
      resources :answers, only: [:edit, :update, :create, :new], shallow: true
    end
  end

spec.rb

before(:each) do
  @user = create_fake_member
  q = create(:questionnaire)
  4.times do
    create(:question, questionnaire: q)
  end
end

27     - fields_for :question, question.create_answer do |answer|

A few things concern me about this line:

1. question.create_answer is going to create a new answer in the database every time a user loads the page, not just when the form is submitted. I think what you want is question.build_answer.
2. fields_for should be called on the form variable f or whatever fields_for fields variable it's nested under.
3. Appending _fields to the fields_for block variable names will help distinguish model instances from field builders.
4. You're saying these are fields for a :question, but then you name the variable answer. These should match. I think instead you want a separate fields_for for each level of russian dolls:

= form_for @questionnaire do |f|
  = @questionnaire.questions.each do |question|
    - f.fields_for :question, question do |question_fields|
      - question_fields.fields_for :answer, question.build_answer do |answer_fields|
        = answer_fields.text_field :description

Maybe that'll get you closer… this is all off the top of my head, untested. For further reading and understanding, these should be helpful:

• fields_for docs
• Nested Attributes Examples