Add tests and add validations

app/models/validations/sales/sale_information_validations.rb

@@ -361,7 +361,12 @@ module Validations::Sales::SaleInformationValidations
 
     if record.firststair == 2 && record.numstair < 2
       record.errors.add :numstair, I18n.t("validations.sales.sale_information.numstair.must_be_greater_than_one")
-      record.errors.add :firststair, I18n.t("validations.sales.sale_information.firststair.more_than_one_transaction")
+      record.errors.add :firststair, I18n.t("validations.sales.sale_information.firststair.cannot_be_no")
+    end
+
+    if record.firststair == 1 && record.numstair > 1
+      record.errors.add :numstair, I18n.t("validations.sales.sale_information.numstair.must_be_one")
+      record.errors.add :firststair, I18n.t("validations.sales.sale_information.firststair.cannot_be_yes")
     end
   end
 

config/locales/validations/sales/sale_information.en.yml

@@ -127,5 +127,7 @@ en:
           value_over_discounted_max: "The percentage discount multiplied by the purchase price is %{discount_value}. This figure should not be more than £102,400 for properties outside of London."
         numstair:
           must_be_greater_than_one: "The number of staircasing transactions must be greater than 1 when this is not the first staircasing transaction."
+          must_be_one: "The number of staircasing transactions must be 1 when this is the first staircasing transaction."
         firststair:
-          more_than_one_transaction: "The answer to 'Is this the first staircasing transaction?' cannot be 'yes' if the number of staircasing transactions is more than 1."
+          cannot_be_no: "The answer to 'Is this the first staircasing transaction?' cannot be 'no' if the number of staircasing transactions is 1."
+          cannot_be_yes: "The answer to 'Is this the first staircasing transaction?' cannot be 'yes' if the number of staircasing transactions is greater than 1."

spec/models/validations/sales/sale_information_validations_spec.rb

@@ -1406,4 +1406,54 @@ RSpec.describe Validations::Sales::SaleInformationValidations do
       end
     end
   end
+
+  describe "#validate_number_of_staircase_transactions" do
+    let(:record) { build(:sales_log, numstair:, firststair:) }
+
+    before do
+      sale_information_validator.validate_number_of_staircase_transactions(record)
+    end
+
+    context "when it is not the first staircasing transaction" do
+      context "and the number of staircasing transactions is between 2 and 10" do
+        let(:numstair) { 6 }
+        let(:firststair) { 2 }
+
+        it "does not add an error" do
+          expect(record.errors).to be_empty
+        end
+      end
+
+      context "and the number of staircasing transactions is less than 2" do
+        let(:numstair) { 1 }
+        let(:firststair) { 2 }
+
+        it "adds an error" do
+          expect(record.errors[:numstair]).to include(I18n.t("validations.sales.sale_information.numstair.must_be_greater_than_one"))
+          expect(record.errors[:firststair]).to include(I18n.t("validations.sales.sale_information.firststair.cannot_be_no"))
+        end
+      end
+    end
+
+    context "when it is the first staircasing transaction" do
+      context "and numstair is also 1" do
+        let(:numstair) { 1 }
+        let(:firststair) { 1 }
+
+        it "does not add an error" do
+          expect(record.errors).to be_empty
+        end
+      end
+
+      context "and numstair is greater than 1" do
+        let(:numstair) { 2 }
+        let(:firststair) { 1 }
+
+        it "adds an error" do
+          expect(record.errors[:numstair]).to include(I18n.t("validations.sales.sale_information.numstair.must_be_one"))
+          expect(record.errors[:firststair]).to include(I18n.t("validations.sales.sale_information.firststair.cannot_be_yes"))
+        end
+      end
+    end
+  end
 end