Add hard validation to cash deposit

app/models/validations/sales/sale_information_validations.rb

@@ -0,0 +1,9 @@
+module Validations::Sales::SaleInformationValidations
+  def validate_deposit_range(record)
+    return if record.deposit.blank?
+
+    unless record.deposit >= 0 && record.deposit <= 999_999
+      record.errors.add :deposit, "Cash deposit must be £0 - £999,999"
+    end
+  end
+end

spec/models/validations/sales/sale_information_validations_spec.rb

@@ -0,0 +1,49 @@
+require "rails_helper"
+
+RSpec.describe Validations::Sales::SaleInformationValidations do
+  subject(:sale_information_validator) { validator_class.new }
+
+  let(:validator_class) { Class.new { include Validations::Sales::SaleInformationValidations } }
+
+  describe "#validate_deposit_range" do
+    context "when within permitted bounds" do
+      let(:record) { build(:sales_log, deposit: 0) }
+
+      it "does not add an error" do
+        sale_information_validator.validate_deposit_range(record)
+
+        expect(record.errors[:deposit]).not_to be_present
+      end
+    end
+
+    context "when blank" do
+      let(:record) { build(:sales_log, deposit: nil) }
+
+      it "does not add an error" do
+        sale_information_validator.validate_deposit_range(record)
+
+        expect(record.errors[:deposit]).not_to be_present
+      end
+    end
+
+    context "when below lower bound" do
+      let(:record) { build(:sales_log, deposit: -1) }
+
+      it "adds an error" do
+        sale_information_validator.validate_deposit_range(record)
+
+        expect(record.errors[:deposit]).to be_present
+      end
+    end
+
+    context "when higher than upper bound" do
+      let(:record) { build(:sales_log, deposit: 1_000_000) }
+
+      it "adds an error" do
+        sale_information_validator.validate_deposit_range(record)
+
+        expect(record.errors[:deposit]).to be_present
+      end
+    end
+  end
+end