rubocop noise: introduced and resolved rails specific cop

http://rubocop.readthedocs.io/en/latest/cops/#rails

app/workers/quiz_status.rb

@@ -14,9 +14,7 @@ class QuizStatus
     candidate.submitted_answers.count == candidate.questions.count
   end
 
-  def completed
-    candidate.completed
-  end
+  delegate :completed, to: :candidate
 
   def can_submit
     on_summary &&