This is because your gems isn't automatically required by bundler
, you can choose of three points:
Either don't use a bundler, and install a gem directly into system, then just require the gem:
require 'FastSpring'
Or use bundler, issue
bundle exec your_code.rb
, in which you've definedrequire 'FastSpring'
, or etc:require 'FastSpring'
Or use bundler, but before all of require instructions, issue
Bundler.require :default
. But this point strongly isn't recommended.Bundler.require :default require 'FastSpring'