IdNumber - Dutch BSN generator

Gemfile.lock

@@ -70,6 +70,7 @@ GEM
 
 PLATFORMS
   arm64-darwin-22
+  arm64-darwin-24
   x86_64-linux
 
 DEPENDENCIES

doc/default/id_number.md

@@ -47,6 +47,9 @@ Faker::IdNumber.danish_id_number(formatted: true) #=> "050390-9980"
 Faker::IdNumber.danish_id_number(birthday: Date.new(1990, 3, 5)) #=> "050390-9980"
 Faker::IdNumber.danish_id_number(gender: :female) #=> "050390-9980"
 
+# Generate a Dutch ID number (BSN)
+Faker::IdNumber.dutch_bsn # => "365371960"
+
 # Generate a valid French Social Security number (INSEE number)
 Faker::IdNumber.french_insee_number #=> "22510589696868"
 ```

lib/faker/default/id_number.rb

@@ -269,6 +269,21 @@ def danish_id_number(formatted: false, birthday: Faker::Date.birthday, gender: n
         ].join
       end
 
+      ##
+      # Produces a random Dutch social security number (Burger Service Nummer).
+      #
+      # @return [String]
+      #
+      # @example
+      #   Faker::IdNumber.dutch_bsn #=> "697116694"
+      #
+      # @faker.version next
+      def dutch_bsn
+        bsn = Faker::Number.numerify('#########') until valid_dutch_bsn?(bsn)
+
+        bsn
+      end
+
       ##
       # Produces a random French social security number (INSEE number).
       #
@@ -416,6 +431,20 @@ def danish_control_digits(birthday)
         end
       end
 
+      def valid_dutch_bsn?(bsn)
+        # If it's not numeric, or not 8 or 9 digits long, it can never be a valid Dutch BSN.
+        return false unless /^\d{8,9}$/.match?(bsn)
+
+        # It must match the BSN-variant of the "Elf Proef" (see https://nl.wikipedia.org/wiki/Elfproef#Burgerservicenummer )
+        sum = 0
+        length = bsn.length
+        bsn.chars.each_with_index do |c, i|
+          sum += c.to_i * (i == length - 1 ? -1 : length - i)
+        end
+
+        (sum % 11).zero?
+      end
+
       def _translate(key)
         parse("id_number.#{key}")
       end

test/faker/default/test_faker_id_number.rb

@@ -274,6 +274,12 @@ def test_danish_id_number_invalid_gender
     end
   end
 
+  def test_dutch_bsn
+    sample = @tester.dutch_bsn
+
+    assert_dutch_bsn sample
+  end
+
   private
 
   def south_african_id_number_to_date_of_birth_string(sample)
@@ -287,4 +293,10 @@ def assert_valid_south_african_id_number(sample)
     assert_equal Faker::IdNumber::ZA_RACE_DIGIT, sample[11]
     assert Date.parse(south_african_id_number_to_date_of_birth_string(sample))
   end
+
+  def assert_dutch_bsn(sample)
+    assert_equal 9, sample.length
+    assert_kind_of String, sample
+    refute_nil Integer(sample)
+  end
 end