diff --git a/lib/dns/tests/update_test.c b/lib/dns/tests/update_test.c
new file mode 100644
index 0000000000..f4f9343f67
--- /dev/null
+++ b/lib/dns/tests/update_test.c
@@ -0,0 +1,275 @@
+/*
+ * Copyright (C) 2011  Internet Systems Consortium, Inc. ("ISC")
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+ * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/* $Id: */
+
+/*! \file */
+
+#include <config.h>
+
+#include <atf-c.h>
+
+#include <unistd.h>
+#include <time.h>
+
+#include <isc/serial.h>
+#include <isc/stdtime.h>
+
+#include <dns/update.h>
+
+#include "dnstest.h"
+
+static isc_uint32_t mystdtime;
+
+static void set_mystdtime(int year, int month, int day) {
+	struct tm tm;
+
+	memset(&tm, 0, sizeof(tm));
+	tm.tm_year = year - 1900;
+	tm.tm_mon = month;
+	tm.tm_mday = day;
+	mystdtime = timegm(&tm) ;
+}
+
+void isc_stdtime_get(isc_stdtime_t *now) {
+	*now = mystdtime;
+}
+
+/*
+ * Individual unit tests
+ */
+
+ATF_TC(increment);
+ATF_TC_HEAD(increment, tc) {
+  atf_tc_set_md_var(tc, "descr", "simple increment by 1");
+}
+ATF_TC_BODY(increment, tc) {
+	isc_uint32_t old = 50;
+	isc_uint32_t new;
+	isc_result_t result;
+
+	UNUSED(tc);
+
+	result = dns_test_begin(NULL);
+	ATF_REQUIRE_EQ(result, ISC_R_SUCCESS);
+	new = dns_update_soaserial(old, dns_updatemethod_increment);
+	ATF_REQUIRE_EQ(isc_serial_lt(old, new), ISC_TRUE);
+	ATF_CHECK(new != 0);
+	ATF_REQUIRE_EQ(new, 51);
+	dns_test_end();
+}
+
+/* 0xfffffffff -> 1 */
+ATF_TC(increment_past_zero);
+ATF_TC_HEAD(increment_past_zero, tc) {
+  atf_tc_set_md_var(tc, "descr", "increment past zero, ffffffff -> 1");
+}
+ATF_TC_BODY(increment_past_zero, tc) {
+	isc_uint32_t old = 0xffffffffu;
+	isc_uint32_t new;
+	isc_result_t result;
+
+	UNUSED(tc);
+
+	result = dns_test_begin(NULL);
+	ATF_REQUIRE_EQ(result, ISC_R_SUCCESS);
+	new = dns_update_soaserial(old, dns_updatemethod_increment);
+	ATF_REQUIRE_EQ(isc_serial_lt(old, new), ISC_TRUE);
+	ATF_CHECK(new != 0);
+	ATF_REQUIRE_EQ(new, 1u);
+	dns_test_end();
+}
+
+ATF_TC(past_to_unix);
+ATF_TC_HEAD(past_to_unix, tc) {
+  atf_tc_set_md_var(tc, "descr", "past to unixtime");
+}
+ATF_TC_BODY(past_to_unix, tc) {
+	isc_uint32_t old;
+	isc_uint32_t new;
+	isc_result_t result;
+
+	UNUSED(tc);
+
+	set_mystdtime(2011, 6, 22);
+	old = mystdtime - 1;
+
+	result = dns_test_begin(NULL);
+	ATF_REQUIRE_EQ(result, ISC_R_SUCCESS);
+	new = dns_update_soaserial(old, dns_updatemethod_unixtime);
+	ATF_REQUIRE_EQ(isc_serial_lt(old, new), ISC_TRUE);
+	ATF_CHECK(new != 0);
+	ATF_REQUIRE_EQ(new, mystdtime);
+	dns_test_end();
+}
+
+ATF_TC(now_to_unix);
+ATF_TC_HEAD(now_to_unix, tc) {
+  atf_tc_set_md_var(tc, "descr", "now to unixtime");
+}
+ATF_TC_BODY(now_to_unix, tc) {
+	isc_uint32_t old;
+	isc_uint32_t new;
+	isc_result_t result;
+
+	UNUSED(tc);
+
+	set_mystdtime(2011, 6, 22);
+	old = mystdtime;
+
+	result = dns_test_begin(NULL);
+	ATF_REQUIRE_EQ(result, ISC_R_SUCCESS);
+	new = dns_update_soaserial(old, dns_updatemethod_unixtime);
+	ATF_REQUIRE_EQ(isc_serial_lt(old, new), ISC_TRUE);
+	ATF_CHECK(new != 0);
+	ATF_REQUIRE_EQ(new, old+1);
+	dns_test_end();
+}
+
+ATF_TC(future_to_unix);
+ATF_TC_HEAD(future_to_unix, tc) {
+  atf_tc_set_md_var(tc, "descr", "future to unixtime");
+}
+ATF_TC_BODY(future_to_unix, tc) {
+	isc_uint32_t old;
+	isc_uint32_t new;
+	isc_result_t result;
+
+	UNUSED(tc);
+
+	set_mystdtime(2011, 6, 22);
+	old = mystdtime + 1;
+
+	result = dns_test_begin(NULL);
+	ATF_REQUIRE_EQ(result, ISC_R_SUCCESS);
+	new = dns_update_soaserial(old, dns_updatemethod_unixtime);
+	ATF_REQUIRE_EQ(isc_serial_lt(old, new), ISC_TRUE);
+	ATF_CHECK(new != 0);
+	ATF_REQUIRE_EQ(new, old+1);
+	dns_test_end();
+}
+
+ATF_TC(undefined_plus1_to_unix);
+ATF_TC_HEAD(undefined_plus1_to_unix, tc) {
+  atf_tc_set_md_var(tc, "descr", "undefined plus 1 to unixtime");
+}
+ATF_TC_BODY(undefined_plus1_to_unix, tc) {
+	isc_uint32_t old;
+	isc_uint32_t new;
+	isc_result_t result;
+
+	UNUSED(tc);
+
+	set_mystdtime(2011, 6, 22);
+	old = mystdtime ^ 0x80000000u;
+	old += 1;
+
+	result = dns_test_begin(NULL);
+	ATF_REQUIRE_EQ(result, ISC_R_SUCCESS);
+	new = dns_update_soaserial(old, dns_updatemethod_unixtime);
+	ATF_REQUIRE_EQ(isc_serial_lt(old, new), ISC_TRUE);
+	ATF_CHECK(new != 0);
+	ATF_REQUIRE_EQ(new, mystdtime);
+	dns_test_end();
+}
+
+ATF_TC(undefined_minus1_to_unix);
+ATF_TC_HEAD(undefined_minus1_to_unix, tc) {
+  atf_tc_set_md_var(tc, "descr", "undefined minus 1 to unixtime");
+}
+ATF_TC_BODY(undefined_minus1_to_unix, tc) {
+	isc_uint32_t old;
+	isc_uint32_t new;
+	isc_result_t result;
+
+	UNUSED(tc);
+
+	set_mystdtime(2011, 6, 22);
+	old = mystdtime ^ 0x80000000u;
+	old -= 1;
+
+	result = dns_test_begin(NULL);
+	ATF_REQUIRE_EQ(result, ISC_R_SUCCESS);
+	new = dns_update_soaserial(old, dns_updatemethod_unixtime);
+	ATF_REQUIRE_EQ(isc_serial_lt(old, new), ISC_TRUE);
+	ATF_CHECK(new != 0);
+	ATF_REQUIRE_EQ(new, old+1);
+	dns_test_end();
+}
+
+ATF_TC(undefined_to_unix);
+ATF_TC_HEAD(undefined_to_unix, tc) {
+  atf_tc_set_md_var(tc, "descr", "undefined to unixtime");
+}
+ATF_TC_BODY(undefined_to_unix, tc) {
+	isc_uint32_t old;
+	isc_uint32_t new;
+	isc_result_t result;
+
+	UNUSED(tc);
+
+	set_mystdtime(2011, 6, 22);
+	old = mystdtime ^ 0x80000000u;
+
+	result = dns_test_begin(NULL);
+	ATF_REQUIRE_EQ(result, ISC_R_SUCCESS);
+	new = dns_update_soaserial(old, dns_updatemethod_unixtime);
+	ATF_REQUIRE_EQ(isc_serial_lt(old, new), ISC_TRUE);
+	ATF_CHECK(new != 0);
+	ATF_REQUIRE_EQ(new, old+1);
+	dns_test_end();
+}
+
+ATF_TC(unixtime_zero);
+ATF_TC_HEAD(unixtime_zero, tc) {
+  atf_tc_set_md_var(tc, "descr", "handle unixtime being zero");
+}
+ATF_TC_BODY(unixtime_zero, tc) {
+	isc_uint32_t old;
+	isc_uint32_t new;
+	isc_result_t result;
+
+	UNUSED(tc);
+
+	mystdtime = 0;
+	old = 0xfffffff0;
+
+	result = dns_test_begin(NULL);
+	ATF_REQUIRE_EQ(result, ISC_R_SUCCESS);
+	new = dns_update_soaserial(old, dns_updatemethod_unixtime);
+	ATF_REQUIRE_EQ(isc_serial_lt(old, new), ISC_TRUE);
+	ATF_CHECK(new != 0);
+	ATF_REQUIRE_EQ(new, old+1);
+	dns_test_end();
+}
+
+/*
+ * Main
+ */
+ATF_TP_ADD_TCS(tp) {
+	ATF_TP_ADD_TC(tp, increment);
+	ATF_TP_ADD_TC(tp, increment_past_zero);
+	ATF_TP_ADD_TC(tp, past_to_unix);
+	ATF_TP_ADD_TC(tp, now_to_unix);
+	ATF_TP_ADD_TC(tp, future_to_unix);
+	ATF_TP_ADD_TC(tp, undefined_to_unix);
+	ATF_TP_ADD_TC(tp, undefined_plus1_to_unix);
+	ATF_TP_ADD_TC(tp, undefined_minus1_to_unix);
+	ATF_TP_ADD_TC(tp, unixtime_zero);
+
+	return (atf_no_error());
+}
+