Use object instead of id for validation

app/models/vote.rb

@@ -6,7 +6,7 @@ class Vote < ApplicationRecord
 
   has_paper_trail ignore: [:updated_at], meta: { conference_id: :conference_id }
 
-  validates :user_id, uniqueness: { scope: :event_id }
+  validates :user, uniqueness: { scope: :event }
 
   delegate :name, to: :user
 

spec/models/vote_spec.rb

@@ -9,9 +9,5 @@ describe Vote do
 
   describe 'validation' do
     it { is_expected.to validate_uniqueness_of(:user_id).scoped_to(:event_id) }
-
-    it 'has a valid factory' do
-      expect(build(:vote)).to be_valid
-    end
   end
 end