if you create a new zone and a record in it for example via
samba-tool dns zonecreate 127.0.0.1 testsite -Uadmin%pwd
samba-tool dns add 127.0.0.1 testsite test A 192.168.1.1 -Uadmin%pwd
then "nslookup test.testsite" gives back NXDOMAIN. After samba restart it is availble though.
*** This bug has been marked as a duplicate of bug 9404 ***