Please don't hardcode the test mode.

If the gateway response doesn't include a live or test indicator then please use the #test? method that's provided by [ActiveMerchant::Billing::Gateway](https://github.com/Shopify/active_merchant/blob/1e8658bc245e1524f4628fe80d76a19001ec1cdc/lib/active_merchant/billing/gateway.rb#L131-L134).

[(example)](https://github.com/Shopify/active_merchant/blob/1e8658bc245e1524f4628fe80d76a19001ec1cdc/lib/active_merchant/billing/gateways/mercury.rb#L288)