Data Migration from prod DB to test DB

Dear Oracle,

I need to import product database DATA into test database.

On prod database server, I got a dmp file (myDATA.dmp).

EXPDP appUser/pwd directory=data_pump_dir dumpfile=myDATA.dmp schemas=appUser content=data_only

On test database,

1. truncate or delete from all table under appUser

2. IMPDP appUser/pwd directory=data_pump_dir dumpfile=myDATA.dmp content=data_only

Data could not imported completely. I got lots of Oracle errors during the IMPDP.

Sample errors,

ORA-31693: Table data object "appUser"."USER_ROLES_OMM_AGENCY" failed to load/unload and is being skipped due to error:
ORA-02291: integrity constraint appUser.FK_OMM_AGE) violated - parent key not found