Fixes iban checksum calculation (#2591)

* Fixes iban checksum calculation * Revisions: Refines wiki comment; Updates test helper method name * Adds iban_checksum test
faker-ruby · Oct 31, 2022 · 5bcdec9 · 5bcdec9
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commit 5bcdec9
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diff --git a/lib/faker/default/bank.rb b/lib/faker/default/bank.rb
@@ -158,15 +158,15 @@ def compile_bsb_number
       end
 
       # Calculates the mandatory checksum in 3rd and 4th characters in IBAN format
-      # source: https://en.wikipedia.org/wiki/International_Bank_Account_Number#Validating_the_IBAN
+      # source: https://en.wikipedia.org/wiki/International_Bank_Account_Number#Generating_IBAN_check_digits
       def iban_checksum(country_code, account)
         # Converts letters to numbers according the iban rules, A=10..Z=35
         account_to_number = "#{account}#{country_code}00".upcase.chars.map do |d|
           d =~ /[A-Z]/ ? (d.ord - 55).to_s : d
         end.join.to_i
 
-        # This is answer to (iban_to_num + checksum) % 97 == 1
-        checksum = (1 - account_to_number) % 97
+        # This is the correct answer to (iban_to_num + checksum) % 97 == 1
+        checksum = 98 - (account_to_number % 97)
 
         # Use leftpad to make the size always to 2
         checksum.to_s.rjust(2, '0')