describe 'embedded 1-1 relations' do
  class Order
    include Mongoid::Document

    embeds_one :address
  end

  class Address
    include Mongoid::Document

    embedded_in :order

    field :city, type: String
  end

  let(:address) { Address.new(city: 'London') }
  let(:order) { Order.create!(address: address) }

  it 'do not call unnecessary unsets' do
    Rails.logger.debug('------- start -------')
    # The below statement results in two updates, the first is unnecessary
    # {"update"=>"orders", "updates"=>[{"q"=>{"_id"=>BSON::ObjectId('58da22a2e9c7a20dba19bf83')}, "u"=>{"$unset"=>{"address"=>true}}, "multi"=>false, "upsert"=>false}], "ordered"=>true}
    # {"update"=>"orders", "updates"=>[{"q"=>{"_id"=>BSON::ObjectId('58da22a2e9c7a20dba19bf83')}, "u"=>{"$set"=>{"address"=>{"_id"=>BSON::ObjectId('58da22a2e9c7a20dba19bf85'), "city"=>"Berlin"}}}, "multi"=>false, "upsert"=>false}], "ordered"=>true}
    order.address = Address.new(city: 'Berlin')
    Rails.logger.debug('------- end -------')
  end
end