An extra test with NULLIF() for MDEV-13995 MAX(timestamp) returns a wrong result near DST change

mysql-test/main/timezone2.result

@@ -574,6 +574,22 @@ a	b
 SELECT * FROM t1 WHERE a IN ((SELECT MAX(b) FROM t1), (SELECT MIN(b) FROM t1));
 a	b
 DROP TABLE t1;
+SET time_zone='Europe/Moscow';
+CREATE TABLE t1 (a TIMESTAMP);
+CREATE TABLE t2 (a TIMESTAMP);
+SET timestamp=1288479599 /*summer time in Mowcow*/;
+INSERT INTO t1 VALUES (CURRENT_TIMESTAMP);
+SET timestamp=1288479599+3600 /*winter time in Mowcow*/;
+INSERT INTO t2 VALUES (CURRENT_TIMESTAMP);
+SELECT t1.a, UNIX_TIMESTAMP(t1.a), t2.a, UNIX_TIMESTAMP(t2.a) FROM t1, t2;
+a	UNIX_TIMESTAMP(t1.a)	a	UNIX_TIMESTAMP(t2.a)
+2010-10-31 02:59:59	1288479599	2010-10-31 02:59:59	1288483199
+SELECT NULLIF(t1.a, t2.a) FROM t1,t2;
+NULLIF(t1.a, t2.a)
+2010-10-31 02:59:59
+DROP TABLE t1, t2;
+SET time_zone=DEFAULT;
+SET timestamp=DEFAULT;
 #
 # MDEV-17979 Assertion `0' failed in Item::val_native upon SELECT with timestamp, NULLIF, GROUP BY
 #

mysql-test/main/timezone2.test

@@ -521,6 +521,23 @@ SELECT * FROM t1 WHERE a = (SELECT MIN(b) FROM t1);
 SELECT * FROM t1 WHERE a IN ((SELECT MAX(b) FROM t1), (SELECT MIN(b) FROM t1));
 DROP TABLE t1;
 
+# NULLIF
+
+SET time_zone='Europe/Moscow';
+
+CREATE TABLE t1 (a TIMESTAMP);
+CREATE TABLE t2 (a TIMESTAMP);
+SET timestamp=1288479599 /*summer time in Mowcow*/;
+INSERT INTO t1 VALUES (CURRENT_TIMESTAMP);
+SET timestamp=1288479599+3600 /*winter time in Mowcow*/;
+INSERT INTO t2 VALUES (CURRENT_TIMESTAMP);
+SELECT t1.a, UNIX_TIMESTAMP(t1.a), t2.a, UNIX_TIMESTAMP(t2.a) FROM t1, t2;
+SELECT NULLIF(t1.a, t2.a) FROM t1,t2;
+DROP TABLE t1, t2;
+SET time_zone=DEFAULT;
+SET timestamp=DEFAULT;
+
+
 --echo #
 --echo # MDEV-17979 Assertion `0' failed in Item::val_native upon SELECT with timestamp, NULLIF, GROUP BY
 --echo #