Prevent School#rejected_at being changed once set

Author: chrisroos

app/models/school.rb

@@ -20,6 +20,7 @@ class School < ApplicationRecord
   validates :rejected_at, absence: { if: proc { |school| school.verified? } }
   validates :verified_at, absence: { if: proc { |school| school.rejected? } }
   validate :verified_at_cannot_be_changed
+  validate :rejected_at_cannot_be_changed
 
   before_validation :normalize_reference
 
@@ -52,4 +53,8 @@ def normalize_reference
   def verified_at_cannot_be_changed
     errors.add(:verified_at, 'cannot be changed after verification') if verified_at_was.present? && verified_at_changed?
   end
+
+  def rejected_at_cannot_be_changed
+    errors.add(:rejected_at, 'cannot be changed after rejection') if rejected_at_was.present? && rejected_at_changed?
+  end
 end

spec/models/school_spec.rb

@@ -195,6 +195,12 @@
       school.update(verified_at: nil)
       expect(school.errors[:verified_at]).to include('cannot be changed after verification')
     end
+
+    it "cannot change #rejected_at once it's been set" do
+      school.update!(rejected_at: Time.zone.now)
+      school.update(rejected_at: nil)
+      expect(school.errors[:rejected_at]).to include('cannot be changed after rejection')
+    end
   end
 
   describe '#creator' do