Now I'm earning my keep.
Trying to get your sample_transaction.rb
up and running I got this error:
➜ activemerchant-demo ruby sample_transaction.rb
/home/nathan/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activemerchant-1.42.6/lib/active_merchant/billing/gateways/authorize_net.rb:288:in `success?': undefined method `exclude?' for ["310", "311"]:Array (NoMethodError)
from /home/nathan/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activemerchant-1.42.6/lib/active_merchant/billing/gateways/authorize_net.rb:278:in `commit'
from /home/nathan/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activemerchant-1.42.6/lib/active_merchant/billing/gateways/authorize_net.rb:117:in `purchase'
from sample_transaction.rb:30:in `<main>'