require 'rails_helper'

RSpec.describe 'mongoid relations' do

  class Post
    include Mongoid::Document

    belongs_to :author
  end

  class Author
    include Mongoid::Document

    field :name, type: String
  end

  context 'when a post gets a new author' do
    it 'does not change the old author' do
      author = Author.create!(name: "old")
      post = Post.new(author: author)
      post.save!

      post.reload
      expect(post.author.name).to eq("old")

      old_author = post.author

      post.author = Author.create!(name: "new")
      post.save!

      new_author = post.author
      expect(new_author.name).to eq("new")
      expect(old_author.name).to eq("old") # boom!
    end
  end
end