Two masters, one slave. All are running MariaDB 10,1.

Slave's my.cnf:
m1.replicate-rewrite-db=testdb->m1testdb
replicate-do-db=m1testdb
replicate-wild-do-table=m1testdb.%

m2.replicate-rewrite-db=testdb->m2testdb
replicate-do-db=m2testdb
replicate-wild-do-table=m2testdb.%

Inserting, updating & deleting on the masters work and changes are replicated to the slave but only when testdb is current db and the table name is unqualified.

insert into testdb.testtable values(1,2,3) <-- Does NOT work whether testdb is current or not
insert into testtable values(1,2,3) <-- Works