You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: pluralization_fallback_test.rb
    path of file: ./repos/i18n/test/backend
    
    the code of the file until where you have to start completion: require 'test_helper'

class I18nBackendPluralizationFallbackTest < I18n::TestCase
  class Backend < I18n::Backend::Simple
    include I18n::Back
    
  def russian_rule
    lambda do |n|
      n ||= 0
      mod10 = n % 10
      mod100 = n % 100

      if mod10 == 1 && mod100 != 11
        :one
      elsif (2..4).include?(mod10) && !(12..14).include?(mod100)
        :few
      elsif mod10 == 0 || (5..9).include?(mod10) || (11..14).include?(mod100)
        :many
      else
        :other
      end
    end