[TD-5707]<test>: add test case

tests/pytest/fulltest.sh

@@ -338,6 +338,7 @@ python3 ./test.py -f functions/function_twa.py -r 1
 python3 ./test.py -f functions/function_twa_test2.py
 python3 ./test.py -f functions/function_stddev_td2555.py
 python3 ./test.py -f functions/showOfflineThresholdIs864000.py
+python3 ./test.py -f functions/function_interp.py
 python3 ./test.py -f insert/metadataUpdate.py
 python3 ./test.py -f query/last_cache.py
 python3 ./test.py -f query/last_row_cache.py

tests/pytest/functions/function_interp.py

@@ -0,0 +1,46 @@
+###################################################################
+#           Copyright (c) 2016 by TAOS Technologies, Inc.
+#                     All rights reserved.
+#
+#  This file is proprietary and confidential to TAOS Technologies.
+#  No part of this file may be reproduced, stored, transmitted,
+#  disclosed or used in any form or by any means other than as
+#  expressly provided by the written permission from Jianhui Tao
+#
+###################################################################
+
+# -*- coding: utf-8 -*-
+
+import sys
+import taos
+from util.log import *
+from util.cases import *
+from util.sql import *
+import numpy as np
+
+
+class TDTestCase:
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor())
+
+        self.rowNum = 10
+        self.ts = 1537146000000
+        
+    def run(self):
+        tdSql.prepare()
+        tdSql.execute("create table t(ts timestamp, k int)")
+        tdSql.execute("insert into t values('2021-1-1 1:1:1', 12);")
+        
+        tdSql.query("select interp(*) from t where ts='2021-1-1 1:1:1'")
+        tdSql.checkRows(1)
+        tdSql.checkData(0, 1, 12)
+
+        tdSql.error("select interp(*) from t where ts >'2021-1-1 1:1:1' and ts < now interval(1s) fill(next)")
+ 
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())