Test for BUG#4889 - inconsistent resilts of more than 2-way natural join

due to incorrect transformation to JOIN ... ON.

The bug itself is fixed by WL#2486.


mysql-test/r/select.result:
  Test for BUG#4889.
mysql-test/t/select.test:
  Test for BUG#4889.

mysql-test/r/select.result

@@ -2860,3 +2860,18 @@ a2	c
 2	2
 drop table t1, t2;
 drop view v2;
+create table t1 (a int(10), t1_val int(10));
+create table t2 (b int(10), t2_val int(10));
+create table t3 (a int(10), b int(10));
+insert into t1 values (1,1),(2,2);
+insert into t2 values (1,1),(2,2),(3,3);
+insert into t3 values (1,1),(2,1),(3,1),(4,1);
+select * from t1 natural join t2 natural join t3;
+a	b	t1_val	t2_val
+1	1	1	1
+2	1	2	1
+select * from t1 natural join t3 natural join t2;
+b	a	t1_val	t2_val
+1	1	1	1
+1	2	2	1
+drop table t1, t2, t3;

mysql-test/t/select.test

@@ -2426,3 +2426,20 @@ select * from v2 natural right join t2;
 
 drop table t1, t2;
 drop view v2;
+
+
+#
+# Bug #4789 Incosistent results of more than 2-way natural joins due to
+#           incorrect transformation to join ... on.
+#
+
+create table t1 (a int(10), t1_val int(10));
+create table t2 (b int(10), t2_val int(10));
+create table t3 (a int(10), b int(10));
+insert into t1 values (1,1),(2,2);
+insert into t2 values (1,1),(2,2),(3,3);
+insert into t3 values (1,1),(2,1),(3,1),(4,1);
+# the following two queries must return the same result
+select * from t1 natural join t2 natural join t3;
+select * from t1 natural join t3 natural join t2;
+drop table t1, t2, t3;