"ORA-00942 : table or view does not exist. " on synonym

"ORA-00942- table or view does not exist" error you are getting , this indicate that user1 does not have privileges on the user.test table (get the details from synonyms SQL which tables are included ) .

We need to grant that required privileges 

SQL> GRANT SELECT, INSERT, UPDATE, DELETE 

     ON USER.TEST 

     TO USER1;

Note : Create dynamic sql to refersh the privelige if multiple tables and schema included