Modify method to add punctuation if needed

app/models/form/question.rb

@@ -204,11 +204,12 @@ class Form::Question
   end
 
   def error_display_label
-    error_label || check_answer_label || header || id.humanize
+    label = error_label || check_answer_label || header || id.humanize
+    label.match?(/[[:punct:]]\z/) && !label.match?(/[(){}\[\]]\z/) ? label : "#{label}."
   end
 
   def unanswered_error_message
-    question_text = error_display_label.presence || "this question"
+    question_text = error_display_label.presence || "this question."
     I18n.t("validations.not_answered", question: question_text.downcase)
   end
 

spec/models/form/question_spec.rb

@@ -375,4 +375,79 @@ RSpec.describe Form::Question, type: :model do
       end
     end
   end
+
+  describe "#error_display_label" do
+    let(:question_with_error_label_no_punctuation) { described_class.new("address_line1_input", { "header" => "Address line 1", "error_label" => "Address line 1" }, page) }
+    let(:question_with_error_label_with_full_stop) { described_class.new("address_line1_input", { "header" => "Address line 1", "error_label" => "Address line 1." }, page) }
+    let(:question_with_error_label_with_question_mark) { described_class.new("address_line1_input", { "header" => "Address line 1", "error_label" => "Address line 1?" }, page) }
+    let(:question_with_error_label_with_brackets) { described_class.new("address_line1_input", { "header" => "Address line 1", "error_label" => "(Address line 1)" }, page) }
+
+    let(:question_with_check_answer_label_no_punctuation) { described_class.new("address_line1_input", { "header" => "Address line 1", "check_answer_label" => "Address line 1" }, page) }
+    let(:question_with_check_answer_label_with_full_stop) { described_class.new("address_line1_input", { "header" => "Address line 1", "check_answer_label" => "Address line 1." }, page) }
+    let(:question_with_check_answer_label_with_question_mark) { described_class.new("address_line1_input", { "header" => "Address line 1", "check_answer_label" => "Address line 1?" }, page) }
+    let(:question_with_check_answer_label_with_brackets) { described_class.new("address_line1_input", { "header" => "Address line 1", "check_answer_label" => "(Address line 1)" }, page) }
+
+    let(:question_with_header_no_punctuation) { described_class.new("address_line1_input", { "header" => "Address line 1" }, page) }
+    let(:question_with_header_with_full_stop) { described_class.new("address_line1_input", { "header" => "Address line 1." }, page) }
+    let(:question_with_header_with_question_mark) { described_class.new("address_line1_input", { "header" => "Address line 1?" }, page) }
+    let(:question_with_header_with_brackets) { described_class.new("address_line1_input", { "header" => "(Address line 1)" }, page) }
+
+    let(:question_with_id_only_no_punctuation) { described_class.new("address_line1_input", {}, page) }
+
+    context "when the error label should stay the same" do
+      it "returns the error label" do
+        expect(question_with_error_label_with_full_stop.error_display_label).to eq("Address line 1.")
+      end
+
+      it "returns the error label" do
+        expect(question_with_error_label_with_question_mark.error_display_label).to eq("Address line 1?")
+      end
+
+      it "returns the error label" do
+        expect(question_with_check_answer_label_with_full_stop.error_display_label).to eq("Address line 1.")
+      end
+
+      it "returns the error label" do
+        expect(question_with_check_answer_label_with_question_mark.error_display_label).to eq("Address line 1?")
+      end
+
+      it "returns the error label" do
+        expect(question_with_header_with_full_stop.error_display_label).to eq("Address line 1.")
+      end
+
+      it "returns the error label" do
+        expect(question_with_header_with_question_mark.error_display_label).to eq("Address line 1?")
+      end
+    end
+
+    context "when the error label should have a full stop added" do
+      it "returns the error label" do
+        expect(question_with_error_label_no_punctuation.error_display_label).to eq("Address line 1.")
+      end
+
+      it "returns the error label" do
+        expect(question_with_error_label_with_brackets.error_display_label).to eq("(Address line 1).")
+      end
+
+      it "returns the error label" do
+        expect(question_with_check_answer_label_no_punctuation.error_display_label).to eq("Address line 1.")
+      end
+
+      it "returns the error label" do
+        expect(question_with_check_answer_label_with_brackets.error_display_label).to eq("(Address line 1).")
+      end
+
+      it "returns the error label" do
+        expect(question_with_header_no_punctuation.error_display_label).to eq("Address line 1.")
+      end
+
+      it "returns the error label" do
+        expect(question_with_header_with_brackets.error_display_label).to eq("(Address line 1).")
+      end
+
+      it "returns the error label" do
+        expect(question_with_id_only_no_punctuation.error_display_label).to eq("Address line1 input.")
+      end
+    end
+  end
 end