Mandatory parameters in mappings

Hello

I am having a mapping where few parameters are mandatory in the target map.I made the MinOccurs and MaxOccurs as 1 for these fields. Still if sometimes the field is missing is source message the mappings executes flawlessly and delivers the file to the target system (my target system is flat file interface) without generating the mandatory field.

Can anyone tell me whether the map will fail at runtime if mandatory parameters did'nt get generated or not? If not then can there be the way to fail the map?

Thanks in advance.

Regards

Rajeev