Copy paste this in your terminal:
echo "rvm 1.8.7@bushidogem-23x-test" > "test_apps/rails-2.3.x-test_app/.rmvrc"
echo "rvm 1.9.2@bushidogem-30x-test" > "test_apps/rails-3.0.x-test_app/.rmvrc"
cd test_apps/rails-2.3.x-test_app && bundle
cd test_apps/rails-3.0.x-test_app && bundle