Remove duplicate errors for check errors page

app/helpers/form_page_error_helper.rb

@@ -4,6 +4,16 @@ module FormPageErrorHelper
     other_page_error_ids.each { |id| lettings_log.errors.delete(id) }
   end
 
+  def remove_duplicate_page_errors(lettings_log)
+    lettings_log.errors.map(&:message)
+    lettings_log.errors.group_by(&:message).each do |_, errors|
+      next if errors.size == 1
+
+      errors.shift
+      errors.each { |error| lettings_log.errors.delete(error.attribute) }
+    end
+  end
+
   def all_questions_affected_by_errors(log)
     log.errors.map(&:attribute) - [:base]
   end

app/views/form/check_errors.html.erb

@@ -2,6 +2,7 @@
   <div class="govuk-grid-column-three-quarters-from-desktop">
 
     <%= form_with model: @log, url: send("#{@log.model_name.param_key}_confirm_clear_answer_path", @log), method: "post", local: true do |f| %>
+      <% remove_duplicate_page_errors(@log) %>
       <%= f.govuk_error_summary %>
       <%= f.hidden_field :page_id, value: @page.id %>
 

spec/helpers/form_page_error_helper_spec.rb

@@ -21,4 +21,22 @@ RSpec.describe FormPageErrorHelper do
       end
     end
   end
+
+  describe "#remove_duplicate_page_errors" do
+    context "when non base other questions are removed" do
+      let!(:lettings_log) { FactoryBot.create(:lettings_log, :in_progress) }
+
+      before do
+        lettings_log.errors.add :layear, "error"
+        lettings_log.errors.add :period, "error_one"
+        lettings_log.errors.add :base, "error_one"
+      end
+
+      it "returns details and user tabs" do
+        remove_duplicate_page_errors(lettings_log)
+        expect(lettings_log.errors.count).to eq(2)
+        expect(lettings_log.errors.map(&:message)).to match_array(%w[error_one error])
+      end
+    end
+  end
 end