Adds possessive-ness to String in a Rails app

possessive.rb

# /lib/yourapp/possessive.rb

module Yourapp
  module Possessive
    # Returns a possessive form of a string
    def possessive
      return self if self.empty?
      self + ('s' == self[-1, 1] ? "'" : "'" + 's')
    end
  end
end

class String
  include Yourapp::Possessive
end

possessive_spec.rb

# /spec/lib/yourapp/possessive_spec.rb

require 'rails_helper'

module Yourapp
  RSpec.describe Possessive do
    describe '.possessive' do
      it 'possessive with a normal string' do
        expect('Brian'.possessive).to eq "Brian's"
      end

      it 'possessive with a string ending with s' do
        expect('Steelers'.possessive).to eq "Steelers'"
      end

      it 'possessive with an empty string' do
        expect(''.possessive).to eq ''
      end
    end
  end
end

yourapp.rb

# /lib/yourapp.rb

require 'yourapp/possessive'