[RSpec] Factorybot trait, making a complex association data

class Author
  has_many :books
  has_many :title_covers, through: :book
end

class Book
  belongs_to :author
  has_many :title_covers
end

class TitleCover
  belongs_to :author
  belongs_to :book
end

FactoryBot.define do
  factory :author, class: Author do

    trait :with_a_book_and_title_covers do
      after(:build) do |author|
        author.books << FactoryBot.build(:book, :with_title_covers)
      end
    end

  end
end

FactoryBot.define do
  factory :book, class: Book do

    trait :with_title_covers do
      after(:build) do |book|
        book.title_covers = FactoryBot.build_list(:title_cover, 2)
      end
    end

  end
end

let(:author){ create(:author, :with_a_book_and_title_covers, name: 'n350071') }