The most simple way to verify correct hash calculation is to use general test credentials, or int other words sandbox testing.

Yleisen testitunnuksen tiedot

When these are used, the service operates in a separate test mode where the orders placed are never saved to database, and for example instead of user actually paying, the service switches to a discrete diagnostics test page. Our service verifies the information content relayed by the web store, and it either reports errors or constructs a reply page in accordance with the interface, or in some cases an XML document.

Generic test credentials are applicable in both production (https://www.maksuturva.fi) and testing addresses (https://test1.maksuturva.fi). Of course we certainly recommend using test addresses for generic testing also.