Implement timezone unit tests for Hesai

Decoders should always decode pointcloud timestamps in UST.
This new unit test decodes the same pointcloud in different timezones
and checks if the decoded times are equal.

nebula_tests/hesai/hesai_ros_decoder_test_main.cpp

@@ -89,6 +89,54 @@ TEST_P(DecoderTest, TestPcd)
   EXPECT_GT(check_cnt, 0);
 }
 
+// Tests if decoders handle timezone settings correctly, i.e. their output timestamps
+// are not affected by timezones and are always output in UST.
+TEST_P(DecoderTest, TestTimezone)
+{
+  // For each pointcloud decoded, this will contain the pointcloud timestamp returned by the driver
+  std::vector<uint64_t> decoded_timestamps;
+
+  auto scan_callback = [&](
+                         uint64_t msg_timestamp, uint64_t scan_timestamp,
+                         nebula::drivers::NebulaPointCloudPtr pointcloud) {
+    if (!pointcloud) return;
+    decoded_timestamps.push_back(scan_timestamp);
+  };
+
+  // First, set the timezone to e.g. GMT, check if setting TZ was successful,
+  // then decode scans and record timestamps
+  setenv("TZ", "/usr/share/zoneinfo/GMT", 1);
+  tzset();
+  ASSERT_STREQ(tzname[0], "GMT");
+  auto gmt = timezone;
+  hesai_driver_->ReadBag(scan_callback);
+
+  // Then, reset driver and timestamps vector for the next decode run
+  TearDown();
+  SetUp();
+  auto decoded_timestamps_cmp = std::vector<uint64_t>(decoded_timestamps);
+  decoded_timestamps.clear();
+
+  // Perform the next run with a different timezone, e.g. JST, check if set successfully,
+  // then decode and record times again
+  setenv("TZ", "/usr/share/zoneinfo/Japan", 1);
+  tzset();
+  ASSERT_STREQ(tzname[0], "JST");
+  auto jst = timezone;
+  hesai_driver_->ReadBag(scan_callback);
+
+  // Wrong timezone settings do not throw an error, they just result in UST+0.
+  // Thus, verify that timezone setting has effect on local timestamp
+  ASSERT_NE(gmt, jst);
+
+  // Assert that the same number (>0) of pointclouds have been decoded,
+  // then compare e.g. the last timestamp to verify that it is not affected
+  // by timezone settings
+  ASSERT_EQ(decoded_timestamps.size(), decoded_timestamps_cmp.size());
+  ASSERT_GT(decoded_timestamps.size(), 0);
+  EXPECT_EQ(decoded_timestamps.back(), decoded_timestamps_cmp.back());
+}
+
 void DecoderTest::SetUp()
 {
   auto decoder_params = GetParam();