Allow to modify the end date as long as it is not to the past

app/models/poll.rb

@@ -39,6 +39,7 @@ class Poll < ApplicationRecord
   validate :date_range
   validate :start_date_is_not_past_date, on: :create
   validate :start_date_change, on: :update
+  validate :end_date_is_not_past_date, on: :update
   validate :only_one_active, unless: :public?
 
   accepts_nested_attributes_for :questions, reject_if: :all_blank, allow_destroy: true
@@ -161,6 +162,12 @@ class Poll < ApplicationRecord
     end
   end
 
+  def end_date_is_not_past_date
+    if will_save_change_to_ends_at? && ends_at < Time.current
+      errors.add(:ends_at, I18n.t("errors.messages.past_date"))
+    end
+  end
+
   def generate_slug?
     slug.nil?
   end

spec/models/poll/poll_spec.rb

@@ -69,6 +69,18 @@ describe Poll do
         poll.starts_at = 10.days.from_now
         expect(poll).not_to be_valid
       end
+
+      it "is valid if changing the end date to a future date" do
+        poll.ends_at = 1.day.from_now
+        expect(poll).to be_valid
+      end
+
+      it "is not valid if changing the end date to a past date" do
+        poll = create(:poll, starts_at: 10.days.ago, ends_at: 10.days.from_now)
+
+        poll.ends_at = 1.day.ago
+        expect(poll).not_to be_valid
+      end
     end
   end