Adding passport validation

app/models/applicants/personal_detail.rb

@@ -19,7 +19,8 @@ class PersonalDetail
     validate :age_less_than_maximum
     validate :minimum_age
     validates :sex, presence: true, inclusion: { in: SEX_OPTIONS }
-    validates :passport_number, presence: true
+    validates :passport_number, presence: true, length: { maximum: 20, message: "passport number is invalid" } # rubocop:disable Rails/I18nLocaleTexts
+    validate :valid_passport_number
     validates :nationality, presence: true, inclusion: { in: NATIONALITIES }
     validates :address_line_1, presence: true
     validates :city, presence: true
@@ -91,6 +92,21 @@ def age_less_than_maximum
       errors.add(:date_of_birth)
     end
 
+    def valid_passport_number
+      return if passport_number.blank?
+
+      # Reject if it contains any characters other than alphanumeric
+      unless /\A[a-zA-Z0-9]+\z/.match?(passport_number)
+        errors.add(:passport_number, "passport number is invalid")
+        return
+      end
+
+      # Reject if it doesn't contain at least one number
+      unless /\d/.match?(passport_number)
+        errors.add(:passport_number, "passport number is invalid")
+      end
+    end
+
     def minimum_age
       # rubocop:disable Rails/Blank
       return unless date_of_birth.present?

app/steps/personal_details_step.rb

@@ -27,6 +27,8 @@ class PersonalDetailsStep < BaseStep
   validates :nationality, inclusion: { in: NATIONALITIES }
   validates :sex, inclusion: { in: SEX_OPTIONS }
   validates :postcode, postcode: true
+  validates :passport_number, length: { maximum: 20, message: "passport number is invalid" } # rubocop:disable Rails/I18nLocaleTexts
+  validate :valid_passport_number
   validate :date_of_birth_not_in_future
   validate :age_less_than_maximum
   validate :minimum_age
@@ -60,6 +62,21 @@ def age_less_than_maximum
     errors.add(:date_of_birth)
   end
 
+  def valid_passport_number
+    return if passport_number.blank?
+
+    # Reject if it contains any characters other than alphanumeric
+    unless /\A[a-zA-Z0-9]+\z/.match?(passport_number)
+      errors.add(:passport_number, "passport number is invalid")
+      return
+    end
+
+    # Reject if it doesn't contain at least one number
+    unless /\d/.match?(passport_number)
+      errors.add(:passport_number, "passport number is invalid")
+    end
+  end
+
   def minimum_age
     # rubocop:disable Rails/Blank
     return unless date_of_birth.present?

spec/models/applicants/personal_detail_spec.rb

@@ -190,6 +190,36 @@ module Applicants
           end
         end
       end
+
+      describe "passport_number validations" do
+        subject(:model) { described_class.new(passport_number:) }
+
+        before { model.valid? }
+
+        context "when passport_number is valid" do
+          valid_passports = %w[PAT34566 A345667 JS3445 434455AFT 2453454]
+
+          valid_passports.each do |valid_passport|
+            let(:passport_number) { valid_passport }
+
+            it "#{valid_passport} should be valid" do
+              expect(model.errors.messages_for(:passport_number)).to be_blank
+            end
+          end
+        end
+
+        context "when passport_number is invalid" do
+          invalid_passports = ["asdfasdf", "nil", "%$^%%^%"]
+
+          invalid_passports.each do |invalid_passport|
+            let(:passport_number) { invalid_passport }
+
+            it "#{invalid_passport} should be invalid" do
+              expect(model.errors.messages_for(:passport_number)).to include("passport number is invalid")
+            end
+          end
+        end
+      end
     end
   end
 end

spec/steps/personal_details_step_spec.rb

@@ -133,5 +133,64 @@
         it { expect(error).to be_blank }
       end
     end
+
+    describe "passport_number" do
+      let(:form) { build(:form, passport_number:) }
+      let(:error) { step.errors.messages_for(:passport_number) }
+
+      before { step.valid? }
+
+      context "numbers and letters" do
+        let(:passport_number) { "AB1234567" }
+
+        it "is valid" do
+          expect(error).to be_blank
+        end
+      end
+
+      context "only numbers" do
+        let(:passport_number) { "123456789" }
+
+        it "is valid" do
+          expect(error).to be_blank
+        end
+      end
+
+      context "only letters" do
+        let(:passport_number) { "ABCDEFGHI" }
+
+        it "is invalid" do
+          expect(error).to be_present
+        end
+      end
+
+      context "other characters" do
+        let(:passport_number) { "&^%$£*()" }
+
+        it "is invalid" do
+          expect(error).to be_present
+        end
+      end
+
+      context "length > 20" do
+        let(:passport_number) { "ABCDEEFGHIJKLMNOPQRSTUVWXYZ1234567890" }
+
+        it "is invalid" do
+          expect(error).to be_present
+        end
+      end
+    end
+
+    describe "private constants" do
+      it "has MAX_AGE set to 80" do
+        max_age = described_class.send(:const_get, :MAX_AGE)
+        expect(max_age).to eq(80)
+      end
+
+      it "has MIN_AGE set to 22" do
+        min_age = described_class.send(:const_get, :MIN_AGE)
+        expect(min_age).to eq(22)
+      end
+    end
   end
 end