"Test Mode" in Authorize.Net and Authorize.Net CIM

[Michael Klett]

I've made a patch that addresses some of the confusion over "test
mode" in Authorize.Net (and CIM) gateways and also allows for easier
co-existence of multiple gateway credentials (some running against the
test gateway, and some against the production gateway) within the same
app.

http://github.com/moklett/active_merchant/commit/4784e80d05f241b02dd9e7eb5957778cc91eee57

First, some background. In the Authorize.Net and Authorize.Net CIM
gateways there are 2 meanings of "test":

1. Test (developers account) gateway vs. Production gateway
2. Test mode, as defined by x_test_request=TRUE on a transaction
request.

Here's some historical threads and discussions about this topic.

http://groups.google.com/group/activemerchant/browse_thread/thread/e7496f471a6e1c7e/64b7ac311c0fe185?lnk=gst&q=test+mode#64b7ac311c0fe185
http://groups.google.com/group/activemerchant/browse_thread/thread/76a3edaad929039f/1d7e1ca1deab59e4?lnk=gst&q=test+mode
http://groups.google.com/group/activemerchant/browse_thread/thread/c4213e022aad264d/d39e768006d8d8f0?lnk=gst&q=test+mode#d39e768006d8d8f0
http://groups.google.com/group/activemerchant/browse_thread/thread/ae38188c02ca9140/bab7020996f38c6f?lnk=gst&q=test+mode#bab7020996f38c6f
http://groups.google.com/group/activemerchant/browse_thread/thread/717680c4b2a77797/dc7af192ff438bc2?lnk=gst&q=test+mode#dc7af192ff438bc2

What I've done in my patch is to document that setting +:test+ to true
does not cause the transaction to run against the test gateway. It
does not change the behavior, and still allows transactions to be sent
with x_test_request=TRUE when setting :test = true on the gateway
initializer.

Additionally, I have allowed for the possibility of specifying which
gateway endpoint to use (:test or :production) in a place other than
the ActiveMerchant::Billing::Base.gateway_mode accessor. This allows
more flexibility in applications where this is considered a variable
value.

I'm open to any feedback and would love to see this accepted in to the
main project.

Thanks,
Michael Klett