# File lib/active_merchant/billing/integrations/hi_trust/helper.rb, line 32
          def amount=(money)
            cents = money.respond_to?(:cents) ? money.cents : money 

            if money.is_a?(String) or cents.to_i < 0
              raise ArgumentError, 'money amount must be either a Money object or a positive integer in cents.' 
            end
            
            add_field(mappings[:amount], cents)
          end