tryメソッド

pre_order.rb

  before_validation :set_company_for_user

  def set_company_for_user
    self.company = self.user.company if self.user.company.present?
  end

このメソッドがある時rspecではここで引っかかるんだけど

pre_order_spec.rb

  describe 'association' do
    subject { FactoryBot.create(:pre_order) }
    context 'belongs_to' do
      it { is_expected.to belong_to(:user) }
    end
  end

tryメソッドに書き換えたら通るようになっただ！

pre_order.rb

  def set_company_for_user
    self.company = self.user.company if self.user.try(:company).present?
  end

参考：https://qiita.com/ngron/items/ec5f72639634949c126e