Just to clarify, the payment sdk's support a "local mode" in which the payment library (in this case bps paymentservice) does not actually contact the paymentsystem (and subsequently the server), for development testing purposes. The default value is false, but the ability needs to be exposed to set development mode to true. We simply need to have a way to tie the setting of the developmentMode property to making a paymentservice_set_connection_mode() call in bps.

It sounds to me like setting it through payment_js should work fine.