I have a RubyGem version 1.2.0 installed on Leopard. If you would like to update RubyGems to a newer version, the RubyGem user guide suggests for modern versions( >0.8.5 ) can use the following command:
gem update --system
But, console told me the 1.2.0 is the latest version - Nothing to update! The work around is to use install rubygem-update:
gem install rubygems-update update_rubygems
Check installed version:
MBP:~ Jay$ gem --version 1.3.1
So now, I'm able to pull the latest rSpec plugin into my Rails project.