Minitest either already includes or auto loads Ruby's own OptionParser
, so that presumably is taking precedence and preventing the loading of your version. Here's evidence:
MacbookAir1:so1 palfvin$ irb
2.0.0p247 :001 > OptionParser
NameError: uninitialized constant OptionParser
from (irb):1
from /Users/palfvin/.rvm/rubies/ruby-2.0.0-p247/bin/irb:16:in `<main>'
2.0.0p247 :002 > require 'minitest'
=> true
2.0.0p247 :003 > OptionParser
=> OptionParser
2.0.0p247 :004 >