Add validation for future start date

app/forms/journeys/early_years_payment/provider/authenticated/start_date_form.rb

@@ -8,7 +8,8 @@ class StartDateForm < Form
           attribute :start_date, :date
 
           validates :start_date, presence: {message: i18n_error_message(:presence)}
-          validate :start_year_has_four_digits, if: -> { start_date.present? }
+          validates :start_date, comparison: {less_than: ->(_) { Date.tomorrow }, message: i18n_error_message(:date_not_in_future)}, if: :start_date
+          validate :start_year_has_four_digits, if: :start_date
 
           def initialize(journey_session:, journey:, params:)
             super
@@ -34,7 +35,7 @@ def nursery_name
 
           def start_year_has_four_digits
             if start_date.year < 1000
-              errors.add(:start_date, "Year must include 4 numbers")
+              errors.add(:start_date, i18n_errors_path(:year_must_have_4_digits))
             end
           end
         end

config/locales/en.yml

@@ -1149,6 +1149,8 @@ en:
         hint: For example, 27 3 2024.
         errors:
           presence: Provide a date in the format 27 3 2024
+          date_not_in_future: Start date cannot be in the future
+          year_must_have_4_digits: Year must include 4 numbers
       child_facing:
         question: Confirm %{first_name} spends most of their time in their job working directly with children
         hint:

spec/forms/journeys/early_years_payment/provider/authenticated/start_date_form_spec.rb

@@ -24,6 +24,16 @@
   describe "validations" do
     it { should validate_presence_of(:start_date).with_message("Provide a date in the format 27 3 2024") }
 
+    context "with a date in the future" do
+      it do
+        is_expected.not_to(
+          allow_value(Date.tomorrow)
+          .for(:start_date)
+          .with_message("Start date cannot be in the future")
+        )
+      end
+    end
+
     context "when the year doesn't have 4 digits" do
       let(:day) { 1 }
       let(:month) { 1 }