tests-extra: refresh -f test

tests-extra/tests/zone/force-refresh/data/example.com.zone

+$ORIGIN example.com.
+$TTL 3600
+
+@	SOA	dns1 hostmaster 2010111201 10800 3600 1209600 7200
+	NS	dns1
+	NS	dns2
+	MX	10 mail
+
+dns1	A	192.0.2.1
+	AAAA	2001:DB8::1
+
+dns2	A	192.0.2.2
+	AAAA	2001:DB8::2
+
+mail	A	192.0.2.3
+	AAAA	2001:DB8::3

tests-extra/tests/zone/force-refresh/data/example.com.zone.1

+$ORIGIN example.com.
+$TTL 3600
+
+@	SOA	dns1 hostmaster 2010111202 10800 3600 1209600 7200
+	NS	dns1
+	NS	dns2
+	MX	10 mail
+
+dns1	A	192.0.2.1
+	AAAA	2001:DB8::1
+
+dns2	A	192.0.2.2
+	AAAA	2001:DB8::2
+
+mail	A	192.0.2.3
+	AAAA	2001:DB8::3
+
+new	A	1.2.3.4

tests-extra/tests/zone/force-refresh/test.py

+#!/usr/bin/env python3
+
+'''Test for reload of a changed zone (serial up, nochange, serial down). '''
+
+from dnstest.test import Test
+from dnstest.utils import set_err, detail_log
+
+t = Test()
+
+master = t.server("bind")
+slave = t.server("knot")
+
+zone = t.zone("example.com.", storage=".")
+t.link(zone, master, slave)
+
+# Load newer zone to the slave
+slave.update_zonefile(zone, version=1)
+
+t.start()
+
+serials_master = master.zones_wait(zone)
+serials_slave = slave.zones_wait(zone)
+
+# Check that the slave's serial is larger than master's
+if serials_master["example.com."] >= serials_slave["example.com."]:
+	set_err("Master has newer or the same zone as slave.")
+
+# Force refresh
+slave.ctl("-f refresh example.com.")
+
+serials_slave = slave.zones_wait(zone)
+compare(serials_slave["example.com."], serials_master["example.com."], "Forced refresh")
+
+t.end()