Eu descobri que não tenho nenhum problema em usarrequire para carregar algo como o framework web Sinatra, mas eu não consigo usarrequire carregar meu próprio código personalizado?

Por exemplo, eu tenho dois arquivos:

test1.rbtest2.rb

O conteúdo do 'test1.rb' é:

#!/usr/bin/env ruby
require 'test2'

O conteúdo do 'test2.rb' é:

class String
    def vowels
        self.scan(/[aeiou]/i)
    end
end

E se eu tentar e correrruby test1.rb então eu recebo o seguinte erro ...

/Users/<username>/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- test2 (LoadError)
    from /Users/<username>/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
    from test1.rb:3:in `<main>'

Então eu notei que se eu tentasse usar oshotgun gem para carregar o servidor web, então eu recebo um rastreamento de pilha diferente, mas mais detalhado do erro ...

Boot Error
Something went wrong while loading test1.rb
LoadError: cannot load such file -- test2

/Users/<username>/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
/Users/<username>/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
/Users/<username>/Dropbox/Library/Ruby/Passage/test1.rb:3:in `<top (required)>'
/Users/<username>/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
/Users/<username>/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/shotgun-0.9/lib/shotgun/loader.rb:114:in `inner_app'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/shotgun-0.9/lib/shotgun/loader.rb:102:in `assemble_app'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/shotgun-0.9/lib/shotgun/loader.rb:86:in `proceed_as_child'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/shotgun-0.9/lib/shotgun/loader.rb:31:in `call!'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/shotgun-0.9/lib/shotgun/loader.rb:18:in `call'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/shotgun-0.9/lib/shotgun/favicon.rb:12:in `call'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/shotgun-0.9/lib/shotgun/static.rb:14:in `call'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/rack-1.4.1/lib/rack/builder.rb:134:in `call'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/thin-1.3.1/lib/thin/connection.rb:80:in `block in pre_process'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/thin-1.3.1/lib/thin/connection.rb:78:in `catch'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/thin-1.3.1/lib/thin/connection.rb:78:in `pre_process'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/thin-1.3.1/lib/thin/connection.rb:53:in `process'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/thin-1.3.1/lib/thin/connection.rb:38:in `receive_data'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/eventmachine-0.12.10/lib/eventmachine.rb:256:in `run_machine'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/eventmachine-0.12.10/lib/eventmachine.rb:256:in `run'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/thin-1.3.1/lib/thin/backends/base.rb:61:in `start'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/thin-1.3.1/lib/thin/server.rb:159:in `start'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/rack-1.4.1/lib/rack/handler/thin.rb:13:in `run'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/gems/shotgun-0.9/bin/shotgun:156:in `<top (required)>'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/bin/shotgun:19:in `load'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/bin/shotgun:19:in `<main>'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/bin/ruby_noexec_wrapper:14:in `eval'
/Users/<username>/.rvm/gems/ruby-1.9.3-p125/bin/ruby_noexec_wrapper:14:in `<main>'

Não tenho certeza qual é o problema?

Qualquer ajuda apreciada por favor.

Obrigado.