expand test: see if another insert fails

ext/db/tests/003.phpt

@@ -8,6 +8,7 @@ DBM Insert/Replace/Fetch Test
 	if (dbmopen($db_file, "n")) {
 		dbminsert($db_file, "key1", "This is a test insert");
 		dbmreplace($db_file, "key1", "This is the replacement text");
+		@dbminsert($db_file, "key1", "This is another replacement text?");
 		$a = dbmfetch($db_file, "key1");
 		dbmclose($db_file);
 		echo $a;