$ORIGIN ext.unit.tests.
@           3600 IN	SOA	ns1.ext.unit.tests. root.ext.unit.tests. (
                        2018071501		; Serial
                        3600    ; Refresh (1 hour)
                        600     ; Retry (10 minutes)
                        604800  ; Expire (1 week)
                        3600    ; NXDOMAIN ttl (1 hour)
                    )

; NS Records
@           3600  IN  NS  ns1.ext.unit.tests.
@           3600  IN  NS  ns2.ext.unit.tests.