diff --git a/perception/traffic_light_fine_detector/CMakeLists.txt b/perception/traffic_light_fine_detector/CMakeLists.txt
index fe9fa2ffcaa8b..e8fe6554f937f 100644
--- a/perception/traffic_light_fine_detector/CMakeLists.txt
+++ b/perception/traffic_light_fine_detector/CMakeLists.txt
@@ -99,6 +99,12 @@ if(TRT_AVAIL AND CUDA_AVAIL AND CUDNN_AVAIL)
     EXECUTABLE traffic_light_fine_detector_node
   )
 
+  if(BUILD_TESTING)
+    ament_auto_add_gtest(traffic_light_fine_detector_tests
+      test/test_nodelet.cpp
+    )
+  endif()
+
   ament_auto_package(INSTALL_TO_SHARE
     launch
     config
diff --git a/perception/traffic_light_fine_detector/include/traffic_light_fine_detector/nodelet.hpp b/perception/traffic_light_fine_detector/include/traffic_light_fine_detector/nodelet.hpp
index 5c89c76a11833..bd145e5026409 100644
--- a/perception/traffic_light_fine_detector/include/traffic_light_fine_detector/nodelet.hpp
+++ b/perception/traffic_light_fine_detector/include/traffic_light_fine_detector/nodelet.hpp
@@ -52,6 +52,9 @@ typedef struct Detection
 
 namespace traffic_light
 {
+float calWeightedIou(
+  const sensor_msgs::msg::RegionOfInterest & bbox1, const tensorrt_yolox::Object & bbox2);
+
 class TrafficLightFineDetectorNodelet : public rclcpp::Node
 {
   using TrafficLightRoi = tier4_perception_msgs::msg::TrafficLightRoi;
diff --git a/perception/traffic_light_fine_detector/src/nodelet.cpp b/perception/traffic_light_fine_detector/src/nodelet.cpp
index 8037dc5472fbe..28f3fafabc6c0 100644
--- a/perception/traffic_light_fine_detector/src/nodelet.cpp
+++ b/perception/traffic_light_fine_detector/src/nodelet.cpp
@@ -27,7 +27,7 @@ namespace fs = ::std::experimental::filesystem;
 #include <utility>
 #include <vector>
 
-namespace
+namespace traffic_light
 {
 float calWeightedIou(
   const sensor_msgs::msg::RegionOfInterest & bbox1, const tensorrt_yolox::Object & bbox2)
@@ -44,10 +44,6 @@ float calWeightedIou(
   return bbox2.score * area1 / area2;
 }
 
-}  // namespace
-
-namespace traffic_light
-{
 inline std::vector<float> toFloatVector(const std::vector<double> double_vector)
 {
   return std::vector<float>(double_vector.begin(), double_vector.end());
@@ -225,7 +221,7 @@ float TrafficLightFineDetectorNodelet::evalMatchScore(
     float max_score = 0.0f;
     const sensor_msgs::msg::RegionOfInterest & expected_roi = roi_p.second.roi;
     for (const tensorrt_yolox::Object & detection : id2detections[tlr_id]) {
-      float score = ::calWeightedIou(expected_roi, detection);
+      float score = calWeightedIou(expected_roi, detection);
       if (score >= max_score) {
         max_score = score;
         id2bestDetection[tlr_id] = detection;
diff --git a/perception/traffic_light_fine_detector/test/test_nodelet.cpp b/perception/traffic_light_fine_detector/test/test_nodelet.cpp
new file mode 100644
index 0000000000000..f45d3351d025d
--- /dev/null
+++ b/perception/traffic_light_fine_detector/test/test_nodelet.cpp
@@ -0,0 +1,55 @@
+// Copyright 2024 TIER IV, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "traffic_light_fine_detector/nodelet.hpp"
+
+#include <gtest/gtest.h>
+
+sensor_msgs::msg::RegionOfInterest createMapBasedBbox(
+  const uint32_t x_offset, const uint32_t y_offset, const uint32_t width, const uint32_t height)
+{
+  sensor_msgs::msg::RegionOfInterest bbox;
+  bbox.x_offset = x_offset;
+  bbox.y_offset = y_offset;
+  bbox.width = width;
+  bbox.height = height;
+  return bbox;
+}
+
+tensorrt_yolox::Object createYoloxBbox(
+  const int32_t x_offset, const int32_t y_offset, const int32_t width, const int32_t height,
+  const float score, const int32_t type)
+{
+  tensorrt_yolox::Object bbox;
+  bbox.x_offset = x_offset;
+  bbox.y_offset = y_offset;
+  bbox.width = width;
+  bbox.height = height;
+  bbox.score = score;
+  bbox.type = type;
+  return bbox;
+}
+
+TEST(CalWeightedIouTest, NoOverlap)
+{
+  const sensor_msgs::msg::RegionOfInterest map_based_bbox = createMapBasedBbox(0, 0, 10, 10);
+  const tensorrt_yolox::Object yolox_bbox = createYoloxBbox(20, 20, 10, 10, 0.9f, 0);
+
+  // check size of map_based_bbox and yolox_bbox
+  EXPECT_EQ(map_based_bbox.width, 10);
+  EXPECT_EQ(yolox_bbox.width, 10);
+  const float iou = traffic_light::calWeightedIou(map_based_bbox, yolox_bbox);
+  EXPECT_FLOAT_EQ(iou, 0.0f);
+  // EXPECT_FLOAT_EQ(traffic_light::calWeightedIou(map_based_bbox, yolox_bbox), 0.0f);
+}