I take full backup with RMAN, after backup I will create tablespace and a user with default tablespace new tablespace and a table on this user schema. After those I loss new tablespace's datafile. RMAN restore datafile without backup of this datafile.
I think, this video will be intersting for Oracle DBA's. You can watch How to restore tablespace in case of NO backup? on youtube.
Mahir M. Quluzade.