For each supported fallback scenario there is information that must be provided to enable to system to simulate a failure. Please note that these considerations are only required for test connections.  Live connections do not require these considerations.

Hosted Payment Form Initialization: Sales Order Header PO number must be ERR01.  This applies to new orders, invoice payments, and authorize/pay by email transactions.

Hosted Payment Form Load: Sales Order Header PO number must be ERR02.  This applies to new orders, invoice payments, and authorize/pay by email transactions.

Hosted Payment Process Result: Sales Order Header PO number must be ERR03. Then, based on the primary connection additional information is required (see below). This applies to new orders, invoice payments, and authorize/pay by email transactions.