Clear none_of_the_above_answer if None of the above not selected

Add a before_validation callback to clear the
`none_of_the_above_answer` for a selection question if 'None of the
above' is not the selected option. This is because we don't want to
include it in the saved answer in this case. This also means that we
no longer need to check the selected option
when applying length validation for `none_of_the_above_answer`.

Author: stephencdaly

app/models/question/selection.rb

@@ -2,10 +2,13 @@ module Question
   class Selection < QuestionBase
     attribute :selection
     attribute :none_of_the_above_answer
+
+    before_validation :clear_none_of_the_above_answer_if_not_selected
+
     validates :selection, presence: true
     validate :selection, :validate_checkbox, if: :allow_multiple_answers?
     validate :selection, :validate_radio, unless: :allow_multiple_answers?
-    validates :none_of_the_above_answer, length: { maximum: 499 }, if: :none_of_the_above_selected?
+    validates :none_of_the_above_answer, length: { maximum: 499 }
 
     with_options unless: :autocomplete_component? do
       validates :none_of_the_above_answer, presence: true, if: :validate_none_of_the_above_answer_presence?
@@ -58,6 +61,10 @@ def has_none_of_the_above_question?
 
   private
 
+    def clear_none_of_the_above_answer_if_not_selected
+      self.none_of_the_above_answer = nil unless none_of_the_above_selected?
+    end
+
     def allowed_options
       selection_options_with_none_of_the_above.map(&:name)
     end

spec/models/question/selection_spec.rb

@@ -338,6 +338,15 @@
               expect(question.errors[:none_of_the_above_answer]).to include(I18n.t("activemodel.errors.models.question/selection.attributes.none_of_the_above_answer.too_long"))
             end
           end
+
+          context "when 'None of the above' is not selected" do
+            it "clears the none_of_the_above_answer before validating" do
+              question.selection = ["option 1"]
+              question.none_of_the_above_answer = "Some answer"
+              expect(question).to be_valid
+              expect(question.none_of_the_above_answer).to be_nil
+            end
+          end
         end
 
         context "when none_of_the_above_question is mandatory" do
@@ -357,6 +366,7 @@
               question.none_of_the_above_answer = "Some answer"
               expect(question).to be_valid
               expect(question.errors[:none_of_the_above_answer]).to be_empty
+              expect(question.none_of_the_above_answer).to eq("Some answer")
             end
           end
 
@@ -375,6 +385,12 @@
               expect(question).to be_valid
               expect(question.errors[:none_of_the_above_answer]).to be_empty
             end
+
+            it "clears the none_of_the_above_answer before validating" do
+              question.none_of_the_above_answer = "Some answer"
+              expect(question).to be_valid
+              expect(question.none_of_the_above_answer).to be_nil
+            end
           end
         end
       end