[TD-2175] add test cases.

src/client/tests/resultFieldTest.cpp

+#include <gtest/gtest.h>
+#include <iostream>
+
+#include "taos.h"
+
+namespace {
+static int64_t start_ts = 1433955661000;
+}
+/* test parse time function */
+TEST(testCase, result_field_test) {
+  taos_options(TSDB_OPTION_CONFIGDIR, "~/first/cfg");
+  taos_init();
+
+  TAOS* conn = taos_connect("ubuntu", "root", "taosdata", 0, 0);
+  if (conn == NULL) {
+    printf("Failed to connect to DB, reason:%s", taos_errstr(conn));
+    exit(-1);
+  }
+
+  TAOS_RES* res = taos_query(conn, "create database if not exists test");
+  ASSERT_EQ(taos_errno(res), 0);
+  taos_free_result(res);
+
+  res = taos_query(conn, "use test");
+  ASSERT_EQ(taos_errno(res), 0);
+  taos_free_result(res);
+
+  res = taos_query(conn, "create table if not exists t1(ts timestamp, k int, a binary(11), b nchar(4))");
+  ASSERT_EQ(taos_errno(res), 0);
+  taos_free_result(res);
+
+  char sql[512] = {0};
+  sprintf(sql, "insert into t1 values(%ld, 99, 'abc', 'test')", start_ts);
+
+  res = taos_query(conn, sql);
+  ASSERT_EQ(taos_errno(res), 0);
+  taos_free_result(res);
+
+  res = taos_query(conn, "select count(*), spread(ts)/(1000 * 3600 * 24), first(a), last(b) from t1");
+  ASSERT_EQ(taos_num_fields(res), 4);
+
+  TAOS_FIELD* fields = taos_fetch_fields(res);
+  ASSERT_EQ(fields[0].bytes, 8);
+  ASSERT_EQ(fields[0].type, TSDB_DATA_TYPE_BIGINT);
+  ASSERT_STREQ(fields[0].name, "count(*)");
+
+  ASSERT_EQ(fields[1].bytes, 8);
+  ASSERT_EQ(fields[1].type, TSDB_DATA_TYPE_DOUBLE);
+  ASSERT_STREQ(fields[1].name, "spread(ts)/(1000 * 3600 * 24)");
+
+  ASSERT_EQ(fields[2].bytes, 11);
+  ASSERT_EQ(fields[2].type, TSDB_DATA_TYPE_BINARY);
+  ASSERT_STREQ(fields[2].name, "first(a)");
+
+  ASSERT_EQ(fields[3].bytes, 4);
+  ASSERT_EQ(fields[3].type, TSDB_DATA_TYPE_NCHAR);
+  ASSERT_STREQ(fields[3].name, "last(b)");
+
+  taos_free_result(res);
+
+  res = taos_query(conn, "select last_row(*) from t1");
+  ASSERT_EQ(taos_num_fields(res), 4);
+
+  fields = taos_fetch_fields(res);
+  ASSERT_EQ(fields[0].bytes, 8);
+  ASSERT_EQ(fields[0].type, TSDB_DATA_TYPE_TIMESTAMP);
+  ASSERT_STREQ(fields[0].name, "last_row(ts)");
+
+  ASSERT_EQ(fields[1].bytes, 4);
+  ASSERT_EQ(fields[1].type, TSDB_DATA_TYPE_INT);
+  ASSERT_STREQ(fields[1].name, "last_row(k)");
+
+  ASSERT_EQ(fields[2].bytes, 11);
+  ASSERT_EQ(fields[2].type, TSDB_DATA_TYPE_BINARY);
+  ASSERT_STREQ(fields[2].name, "last_row(a)");
+
+  ASSERT_EQ(fields[3].bytes, 4);
+  ASSERT_EQ(fields[3].type, TSDB_DATA_TYPE_NCHAR);
+  ASSERT_STREQ(fields[3].name, "last_row(b)");
+
+  taos_free_result(res);
+  res = taos_query(conn, "select first(*), last(*) from t1");
+  ASSERT_EQ(taos_num_fields(res), 8);
+
+  fields = taos_fetch_fields(res);
+  ASSERT_EQ(fields[0].bytes, 8);
+  ASSERT_EQ(fields[0].type, TSDB_DATA_TYPE_TIMESTAMP);
+  ASSERT_STREQ(fields[0].name, "first(ts)");
+
+  ASSERT_EQ(fields[1].bytes, 4);
+  ASSERT_EQ(fields[1].type, TSDB_DATA_TYPE_INT);
+  ASSERT_STREQ(fields[1].name, "first(k)");
+
+  ASSERT_EQ(fields[2].bytes, 11);
+  ASSERT_EQ(fields[2].type, TSDB_DATA_TYPE_BINARY);
+  ASSERT_STREQ(fields[2].name, "first(a)");
+
+  ASSERT_EQ(fields[3].bytes, 4);
+  ASSERT_EQ(fields[3].type, TSDB_DATA_TYPE_NCHAR);
+  ASSERT_STREQ(fields[3].name, "first(b)");
+
+  taos_free_result(res);
+
+  res = taos_query(conn, "select first(ts, a, k, k, b, b, ts) from t1");
+  ASSERT_EQ(taos_num_fields(res), 7);
+
+  fields = taos_fetch_fields(res);
+  ASSERT_EQ(fields[0].bytes, 8);
+  ASSERT_EQ(fields[0].type, TSDB_DATA_TYPE_TIMESTAMP);
+  ASSERT_STREQ(fields[0].name, "first(ts)");
+
+  ASSERT_EQ(fields[1].bytes, 11);
+  ASSERT_EQ(fields[1].type, TSDB_DATA_TYPE_BINARY);
+  ASSERT_STREQ(fields[1].name, "first(a)");
+
+  ASSERT_EQ(fields[2].bytes, 4);
+  ASSERT_EQ(fields[2].type, TSDB_DATA_TYPE_INT);
+  ASSERT_STREQ(fields[2].name, "first(k)");
+
+  ASSERT_EQ(fields[3].bytes, 4);
+  ASSERT_EQ(fields[3].type, TSDB_DATA_TYPE_INT);
+  ASSERT_STREQ(fields[3].name, "first(k)");
+
+  ASSERT_EQ(fields[4].bytes, 4);
+  ASSERT_EQ(fields[4].type, TSDB_DATA_TYPE_NCHAR);
+  ASSERT_STREQ(fields[4].name, "first(b)");
+
+  ASSERT_EQ(fields[5].bytes, 4);
+  ASSERT_EQ(fields[5].type, TSDB_DATA_TYPE_NCHAR);
+  ASSERT_STREQ(fields[5].name, "first(b)");
+
+  ASSERT_EQ(fields[6].bytes, 8);
+  ASSERT_EQ(fields[6].type, TSDB_DATA_TYPE_TIMESTAMP);
+  ASSERT_STREQ(fields[6].name, "first(ts)");
+
+  taos_free_result(res);
+  taos_close(conn);
+}