Test the workflow by submitting the web form. You get the URL for the web form directly after publishing.
Please note that input values have to be in SAP-compliant format. If you haven’t entered conversion routines for Delivery Date and Cost Center you have to enter these fields in an SAP-compliant manner (“yyyyMMdd” for the date format and leading zeros for the 10 digits cost center).
You can see in the workflow’s instance details if it was completed and if the result parameter was logged sucessfully. Then you can be sure that the purchase requisition was created in SAP.