progress on #27: test coverage over 96%

app/models/candidate.rb

@@ -37,6 +37,9 @@ class Candidate < ApplicationRecord
     "#{my_status.progress}%"
   end
 
+  # FIXME: This feels wrong here. Mail deliveries should be in controller.
+  #        Privatize in QuizController
+  #        also, bang methods in ruby do an action and replace, or return nil
   def complete!
     if update_attributes(completed: true)
       CandidateMailer.submitted(self).deliver_now