Why do I get an uninitialized constant Test::Unit::AutoRunner::Priority error?

I am upgrading to Ruby 1.9.2, and getting the following error:

/workspace/current/upgrade1.9.2/vendor/rails/activesupport/lib/active_support/dependencies.rb:131:in `rescue in const_missing': uninitialized constant Test::Unit::AutoRunner::Priority
/vendor/rails/activesupport/lib/active_support/dependencies.rb:120:in `const_missing'
from /.rvm/gems/ruby-1.9.2-p180@ruby-192-upgrade192/gems/test-unit-2.2.0/lib/test/unit/autorunner.rb:257:in `block in options'
from /.rvm/rubies/ru开发者_如何学Pythonby-1.9.2-p180/lib/ruby/1.9.1/optparse.rb:799:in `initialize'
from /.rvm/gems/ruby-1.9.2-p180@ruby-192-upgrade192/gems/test-unit-2.2.0/lib/test/unit/autorunner.rb:151:in `new'
from /.rvm/gems/ruby-1.9.2-p180@ruby-192-upgrade192/gems/test-unit-2.2.0/lib/test/unit/autorunner.rb:151:in `options'
from /.rvm/gems/ruby-1.9.2-p180@ruby-192-upgrade192/gems/test-unit-2.2.0/lib/test/unit/autorunner.rb:141:in `process_args'
from /.rvm/gems/ruby-1.9.2-p180@ruby-192-upgrade192/gems/test-unit-2.2.0/lib/test/unit/autorunner.rb:57:in `run'
from /Users/avijayendra/.rvm/gems/ruby-1.9.2-p180@ruby-192-upgrade192/gems/test-unit-2.2.0/lib/test/unit.rb:326:in `block in <top (required)>'

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Gems aren't automatically carried over between Ruby versions when you upgrade through RVM. If you haven't defined the Gem as global, reinstall the necessary gems while using the new Ruby version.