diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 0ba3096..f7ff60b 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -14,7 +14,14 @@ repos:
     hooks:
       - id: ruff
         name: ruff
-        entry: ruff check .
-        language: python
+        entry: uv run ruff check .
+        language: system
         types: [python]
+        always_run: true
+
+      - id: pytest
+        name: pytest
+        entry: uv run pytest tests/ -v
+        language: system
+        pass_filenames: false
         always_run: true
\ No newline at end of file
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..ee8344c
--- /dev/null
+++ b/tests/__init__.py
@@ -0,0 +1 @@
+# __init__.py for tests package
diff --git a/tests/test_gpx.py b/tests/test_gpx.py
new file mode 100644
index 0000000..252fdbb
--- /dev/null
+++ b/tests/test_gpx.py
@@ -0,0 +1,268 @@
+# test_gpx.py
+#
+# author: deng
+# date: 20251129
+
+import io
+
+import pytest
+
+
+class TestGPXProcessor:
+    """Test cases for GPXProcessor class."""
+
+    @pytest.fixture
+    def simple_gpx_data(self):
+        """Create a simple GPX file data for testing."""
+        gpx_xml = """<?xml version="1.0" encoding="UTF-8"?>
+            <gpx version="1.1" creator="test">
+              <wpt lat="25.0" lon="121.0">
+                <ele>100</ele>
+                <name>Test Waypoint</name>
+              </wpt>
+              <trk>
+                <name>Test Track</name>
+                <trkseg>
+                  <trkpt lat="25.0" lon="121.0">
+                    <ele>100</ele>
+                    <time>2024-01-01T00:00:00Z</time>
+                  </trkpt>
+                  <trkpt lat="25.001" lon="121.001">
+                    <ele>150</ele>
+                    <time>2024-01-01T00:01:00Z</time>
+                  </trkpt>
+                  <trkpt lat="25.002" lon="121.002">
+                    <ele>120</ele>
+                    <time>2024-01-01T00:02:00Z</time>
+                  </trkpt>
+                </trkseg>
+              </trk>
+            </gpx>"""
+        return io.BytesIO(gpx_xml.encode('utf-8'))
+
+    @pytest.fixture
+    def gpx_processor(self, simple_gpx_data):
+        """Create a GPXProcessor instance with simple data."""
+        from hiking_assistant.gpx import GPXProcessor
+
+        processor = GPXProcessor(simple_gpx_data)
+        processor.validate_and_parse()
+        return processor
+
+    def test_init(self):
+        """Test GPXProcessor initialization."""
+        from hiking_assistant.gpx import GPXProcessor
+
+        gpx_file = io.BytesIO(b'test data')
+        processor = GPXProcessor(gpx_file)
+
+        assert processor.gpx_file == gpx_file
+        assert processor.gpx is None
+        assert processor.points == []
+        assert processor.elevations == []
+        assert processor.waypoints == []
+
+    def test_validate_and_parse_success(self, simple_gpx_data):
+        """Test successful GPX parsing."""
+        from hiking_assistant.gpx import GPXProcessor
+
+        processor = GPXProcessor(simple_gpx_data)
+        result = processor.validate_and_parse()
+
+        assert result is True
+        assert len(processor.points) == 3
+        assert len(processor.elevations) == 3
+        assert len(processor.waypoints) == 1
+
+    def test_validate_and_parse_invalid_gpx_raises_exception(self):
+        """Test that invalid GPX data raises exception."""
+        from hiking_assistant.gpx import GPXProcessor
+
+        invalid_data = io.BytesIO(b'not a valid gpx file')
+        processor = GPXProcessor(invalid_data)
+
+        with pytest.raises(Exception, match='GPX 檔案解析失敗'):
+            processor.validate_and_parse()
+
+    def test_waypoint_extraction(self, gpx_processor):
+        """Test waypoint extraction from GPX."""
+        assert len(gpx_processor.waypoints) == 1
+        waypoint = gpx_processor.waypoints[0]
+        assert waypoint['lat'] == 25.0
+        assert waypoint['lon'] == 121.0
+        assert waypoint['name'] == 'Test Waypoint'
+        assert waypoint['elevation'] == 100.0
+
+    def test_calculate_distance(self, gpx_processor):
+        """Test distance calculation."""
+        distance = gpx_processor.calculate_distance()
+
+        assert distance > 0
+        assert isinstance(distance, float)
+        assert len(gpx_processor.distances) == 3
+        assert gpx_processor.distances[0] == 0.0
+
+    def test_calculate_distance_empty_points_returns_zero(self):
+        """Test distance calculation with no points."""
+        from hiking_assistant.gpx import GPXProcessor
+
+        processor = GPXProcessor(io.BytesIO(b''))
+        distance = processor.calculate_distance()
+
+        assert distance == 0.0
+
+    def test_calculate_elevation_gain_loss(self, gpx_processor):
+        """Test elevation gain/loss calculation."""
+        gain, loss = gpx_processor.calculate_elevation_gain_loss()
+
+        assert isinstance(gain, float)
+        assert isinstance(loss, float)
+        assert gain >= 0
+        assert loss >= 0
+
+    def test_get_min_max_elevation(self, gpx_processor):
+        """Test min/max elevation retrieval."""
+        min_elev, max_elev = gpx_processor.get_min_max_elevation()
+
+        assert min_elev == 100.0
+        assert max_elev == 150.0
+
+    def test_get_min_max_elevation_empty_returns_zero(self):
+        """Test min/max elevation with empty data."""
+        from hiking_assistant.gpx import GPXProcessor
+
+        processor = GPXProcessor(io.BytesIO(b''))
+        min_elev, max_elev = processor.get_min_max_elevation()
+
+        assert min_elev == 0.0
+        assert max_elev == 0.0
+
+    def test_get_start_end_points(self, gpx_processor):
+        """Test start/end points retrieval."""
+        start, end = gpx_processor.get_start_end_points()
+
+        assert start == (25.0, 121.0, 100.0)
+        assert end == (25.002, 121.002, 120.0)
+
+    def test_get_start_end_points_insufficient_data_returns_none(self):
+        """Test start/end points with insufficient data."""
+        from hiking_assistant.gpx import GPXProcessor
+
+        processor = GPXProcessor(io.BytesIO(b''))
+        start, end = processor.get_start_end_points()
+
+        assert start is None
+        assert end is None
+
+    def test_get_all_points(self, gpx_processor):
+        """Test getting all route points."""
+        points = gpx_processor.get_all_points()
+
+        assert len(points) == 3
+        assert all(isinstance(p, tuple) and len(p) == 2 for p in points)
+
+    def test_get_elevation_profile_data(self, gpx_processor):
+        """Test elevation profile data retrieval."""
+        # Need to calculate distances first
+        gpx_processor.calculate_distance()
+        distances, elevations = gpx_processor.get_elevation_profile_data()
+
+        assert len(distances) == len(elevations)
+        assert len(distances) == 3
+
+    def test_get_gradients(self, gpx_processor):
+        """Test gradient calculation."""
+        gradients = gpx_processor.get_gradients()
+
+        assert len(gradients) == 2  # n-1 gradients for n points
+        assert all(isinstance(g, (int, float)) for g in gradients)
+
+    def test_get_gradients_empty_returns_empty_list(self):
+        """Test gradient calculation with no points."""
+        from hiking_assistant.gpx import GPXProcessor
+
+        processor = GPXProcessor(io.BytesIO(b''))
+        gradients = processor.get_gradients()
+
+        assert gradients == []
+
+    def test_calculate_naismith_time(self, gpx_processor):
+        """Test Naismith's Rule time calculation."""
+        time_minutes = gpx_processor.calculate_naismith_time()
+
+        assert isinstance(time_minutes, int)
+        assert time_minutes >= 0
+
+    def test_calculate_naismith_time_with_custom_speeds(self, gpx_processor):
+        """Test Naismith calculation with custom speeds."""
+        time_default = gpx_processor.calculate_naismith_time()
+        time_fast = gpx_processor.calculate_naismith_time(horizontal_speed=10, vertical_speed=1200)
+
+        # Faster speeds should result in less time
+        assert time_fast < time_default
+
+    def test_calculate_naismith_time_no_points_returns_zero(self):
+        """Test Naismith calculation with no points."""
+        from hiking_assistant.gpx import GPXProcessor
+
+        processor = GPXProcessor(io.BytesIO(b''))
+        time_minutes = processor.calculate_naismith_time()
+
+        assert time_minutes == 0
+
+
+class TestGPXProcessorEdgeCases:
+    """Test edge cases for GPXProcessor."""
+
+    def test_gpx_with_bytes_data(self):
+        """Test GPX parsing with bytes input."""
+        from hiking_assistant.gpx import GPXProcessor
+
+        gpx_xml = b"""<?xml version="1.0" encoding="UTF-8"?>
+            <gpx version="1.1">
+              <trk>
+                <trkseg>
+                  <trkpt lat="25.0" lon="121.0"><ele>100</ele></trkpt>
+                </trkseg>
+              </trk>
+            </gpx>"""
+        processor = GPXProcessor(io.BytesIO(gpx_xml))
+        result = processor.validate_and_parse()
+
+        assert result is True
+
+    def test_gpx_with_string_data(self):
+        """Test GPX parsing with string input."""
+        from hiking_assistant.gpx import GPXProcessor
+
+        gpx_xml = """<?xml version="1.0" encoding="UTF-8"?>
+            <gpx version="1.1">
+              <trk>
+                <trkseg>
+                  <trkpt lat="25.0" lon="121.0"><ele>100</ele></trkpt>
+                </trkseg>
+              </trk>
+            </gpx>"""
+        processor = GPXProcessor(io.StringIO(gpx_xml))
+        result = processor.validate_and_parse()
+
+        assert result is True
+
+    def test_gpx_with_no_elevation_data(self):
+        """Test GPX parsing when elevation data is missing."""
+        from hiking_assistant.gpx import GPXProcessor
+
+        gpx_xml = """<?xml version="1.0" encoding="UTF-8"?>
+            <gpx version="1.1">
+              <trk>
+                <trkseg>
+                  <trkpt lat="25.0" lon="121.0"></trkpt>
+                  <trkpt lat="25.001" lon="121.001"></trkpt>
+                </trkseg>
+              </trk>
+            </gpx>"""
+        processor = GPXProcessor(io.BytesIO(gpx_xml.encode('utf-8')))
+        processor.validate_and_parse()
+
+        # Should default to 0 elevation
+        assert all(e == 0 for e in processor.elevations)
diff --git a/tests/test_utils.py b/tests/test_utils.py
new file mode 100644
index 0000000..17684ec
--- /dev/null
+++ b/tests/test_utils.py
@@ -0,0 +1,62 @@
+# test_utils.py
+#
+# author: deng
+# date: 20251129
+
+import base64
+import tempfile
+from pathlib import Path
+
+import pytest
+
+
+class TestConvertImageToBase64:
+    """Test cases for convert_image_to_base64 function."""
+
+    @pytest.fixture
+    def temp_image_file(self):
+        """Create a temporary image file for testing."""
+        with tempfile.NamedTemporaryFile(mode='wb', suffix='.jpg', delete=False) as f:
+            # Create a simple test image (1x1 red pixel)
+            f.write(b'\xff\xd8\xff\xe0\x00\x10JFIF')  # JPEG header
+            temp_path = f.name
+        yield temp_path
+        # Cleanup
+        Path(temp_path).unlink(missing_ok=True)
+
+    def test_convert_image_to_base64_returns_string(self, temp_image_file):
+        """Test that function returns a string."""
+        from hiking_assistant.utils import convert_image_to_base64
+
+        result = convert_image_to_base64(temp_image_file)
+        assert isinstance(result, str)
+
+    def test_convert_image_to_base64_returns_valid_base64(self, temp_image_file):
+        """Test that returned string is valid base64."""
+        from hiking_assistant.utils import convert_image_to_base64
+
+        result = convert_image_to_base64(temp_image_file)
+        # Try to decode - should not raise exception
+        decoded = base64.b64decode(result)
+        assert isinstance(decoded, bytes)
+
+    def test_convert_image_to_base64_roundtrip(self, temp_image_file):
+        """Test roundtrip conversion (file -> base64 -> binary)."""
+        from hiking_assistant.utils import convert_image_to_base64
+
+        # Read original file
+        with open(temp_image_file, 'rb') as f:
+            original_data = f.read()
+
+        # Convert to base64 and back
+        base64_str = convert_image_to_base64(temp_image_file)
+        decoded_data = base64.b64decode(base64_str)
+
+        assert decoded_data == original_data
+
+    def test_convert_image_to_base64_nonexistent_file_raises_error(self):
+        """Test that function raises error for non-existent file."""
+        from hiking_assistant.utils import convert_image_to_base64
+
+        with pytest.raises(FileNotFoundError):
+            convert_image_to_base64('/nonexistent/path/to/image.jpg')
diff --git a/tests/test_weather.py b/tests/test_weather.py
new file mode 100644
index 0000000..cbbba57
--- /dev/null
+++ b/tests/test_weather.py
@@ -0,0 +1,262 @@
+# test_weather.py
+#
+# author: deng
+# date: 20251129
+
+from unittest.mock import Mock, patch
+
+import pytest
+import requests
+
+
+class TestWeatherFetcher:
+    """Test cases for WeatherFetcher class."""
+
+    @pytest.fixture
+    def weather_fetcher(self):
+        """Create a WeatherFetcher instance."""
+        from hiking_assistant.weather import WeatherFetcher
+
+        return WeatherFetcher()
+
+    @pytest.fixture
+    def mock_weather_response(self):
+        """Mock weather API response data."""
+        return {
+            'current': {
+                'relative_humidity_2m': 75,
+                'apparent_temperature': 18.5,
+                'precipitation_probability': 30,
+                'precipitation': 0.5,
+                'wind_speed_10m': 15.2,
+                'wind_direction_10m': 180,
+            },
+            'daily': {
+                'temperature_2m_max': [22.0, 23.5, 21.0],
+                'temperature_2m_min': [15.0, 16.0, 14.5],
+                'apparent_temperature_max': [20.0, 21.5, 19.0],
+                'apparent_temperature_min': [13.0, 14.0, 12.5],
+                'relative_humidity_2m_mean': [70, 75, 68],
+                'precipitation_sum': [0.0, 2.5, 0.0],
+                'precipitation_probability_max': [20, 60, 15],
+                'wind_speed_10m_max': [25.0, 35.0, 20.0],
+                'wind_direction_10m_dominant': [180, 90, 270],
+                'sunrise': ['2024-01-01T06:00:00', '2024-01-02T06:01:00', '2024-01-03T06:02:00'],
+                'sunset': ['2024-01-01T18:00:00', '2024-01-02T18:01:00', '2024-01-03T18:02:00'],
+                'uv_index_max': [5.0, 7.0, 3.0],
+                'time': ['2024-01-01', '2024-01-02', '2024-01-03'],
+            },
+        }
+
+    def test_init_default_values(self):
+        """Test WeatherFetcher initialization with defaults."""
+        from hiking_assistant.weather import WeatherFetcher
+
+        fetcher = WeatherFetcher()
+
+        assert fetcher.api_url == 'https://api.open-meteo.com/v1/forecast'
+        assert fetcher.request_timeout == 8
+        assert fetcher.forecast_days == 7
+
+    def test_init_custom_values(self):
+        """Test WeatherFetcher initialization with custom values."""
+        from hiking_assistant.weather import WeatherFetcher
+
+        fetcher = WeatherFetcher(api_url='https://custom.api.com', request_timeout=10, forecast_days=3)
+
+        assert fetcher.api_url == 'https://custom.api.com'
+        assert fetcher.request_timeout == 10
+        assert fetcher.forecast_days == 3
+
+    def test_convert_wind_degrees_to_flow_direction_north(self, weather_fetcher):
+        """Test wind direction conversion for north."""
+        result = weather_fetcher.convert_wind_degrees_to_flow_direction(0)
+        assert result in ['⬇️', '⬆️']  # 0 and 360 degrees
+
+    def test_convert_wind_degrees_to_flow_direction_east(self, weather_fetcher):
+        """Test wind direction conversion for east."""
+        result = weather_fetcher.convert_wind_degrees_to_flow_direction(90)
+        assert result == '⬅️'  # 90 degrees = east wind blowing west
+
+    def test_convert_wind_degrees_to_flow_direction_south(self, weather_fetcher):
+        """Test wind direction conversion for south."""
+        result = weather_fetcher.convert_wind_degrees_to_flow_direction(180)
+        assert result == '⬆️'
+
+    def test_convert_wind_degrees_to_flow_direction_west(self, weather_fetcher):
+        """Test wind direction conversion for west."""
+        result = weather_fetcher.convert_wind_degrees_to_flow_direction(270)
+        assert result == '➡️'  # 270 degrees = west wind blowing east
+
+    def test_convert_wind_degrees_to_flow_direction_none(self, weather_fetcher):
+        """Test wind direction conversion with None input."""
+        result = weather_fetcher.convert_wind_degrees_to_flow_direction(None)
+        assert result == 'N/A'
+
+    def test_get_wind_speed_indicator_safe(self, weather_fetcher):
+        """Test wind speed indicator for safe level."""
+        result = weather_fetcher.get_wind_speed_indicator(15)
+        assert result == '🟢'
+
+    def test_get_wind_speed_indicator_caution(self, weather_fetcher):
+        """Test wind speed indicator for caution level."""
+        result = weather_fetcher.get_wind_speed_indicator(30)
+        assert result == '🟡'
+
+    def test_get_wind_speed_indicator_alert(self, weather_fetcher):
+        """Test wind speed indicator for alert level."""
+        result = weather_fetcher.get_wind_speed_indicator(50)
+        assert result == '🟠'
+
+    def test_get_wind_speed_indicator_dangerous(self, weather_fetcher):
+        """Test wind speed indicator for dangerous level."""
+        result = weather_fetcher.get_wind_speed_indicator(65)
+        assert result == '🔴'
+
+    def test_get_wind_speed_indicator_none(self, weather_fetcher):
+        """Test wind speed indicator with None input."""
+        result = weather_fetcher.get_wind_speed_indicator(None)
+        assert result == ''
+
+    def test_get_uv_index_indicator_low(self, weather_fetcher):
+        """Test UV index indicator for low level."""
+        result = weather_fetcher.get_uv_index_indicator(2)
+        assert result == '🟢'
+
+    def test_get_uv_index_indicator_moderate(self, weather_fetcher):
+        """Test UV index indicator for moderate level."""
+        result = weather_fetcher.get_uv_index_indicator(4)
+        assert result == '🟡'
+
+    def test_get_uv_index_indicator_high(self, weather_fetcher):
+        """Test UV index indicator for high level."""
+        result = weather_fetcher.get_uv_index_indicator(6)
+        assert result == '🟠'
+
+    def test_get_uv_index_indicator_very_high(self, weather_fetcher):
+        """Test UV index indicator for very high level."""
+        result = weather_fetcher.get_uv_index_indicator(9)
+        assert result == '🔴'
+
+    def test_get_uv_index_indicator_extreme(self, weather_fetcher):
+        """Test UV index indicator for extreme level."""
+        result = weather_fetcher.get_uv_index_indicator(11)
+        assert result == '🟣'
+
+    def test_get_uv_index_indicator_none(self, weather_fetcher):
+        """Test UV index indicator with None input."""
+        result = weather_fetcher.get_uv_index_indicator(None)
+        assert result == ''
+
+    @patch('hiking_assistant.weather.requests.get')
+    def test_get_weather_success(self, mock_get, weather_fetcher, mock_weather_response):
+        """Test successful weather data retrieval."""
+        mock_response = Mock()
+        mock_response.json.return_value = mock_weather_response
+        mock_get.return_value = mock_response
+
+        result = weather_fetcher.get_weather(25.0, 121.0)
+
+        assert result is not None
+        assert 'current_humidity' in result
+        assert 'daily_temp_max' in result
+        assert result['current_humidity'] == 75
+        assert len(result['daily_temp_max']) == 3
+
+    @patch('hiking_assistant.weather.requests.get')
+    def test_get_weather_request_exception(self, mock_get, weather_fetcher):
+        """Test weather retrieval with request exception."""
+        mock_get.side_effect = requests.exceptions.RequestException('Connection error')
+
+        result = weather_fetcher.get_weather(25.0, 121.0)
+
+        assert result is None
+
+    @patch('hiking_assistant.weather.requests.get')
+    def test_get_weather_json_parsing_error(self, mock_get, weather_fetcher):
+        """Test weather retrieval with JSON parsing error."""
+        mock_response = Mock()
+        mock_response.json.side_effect = ValueError('Invalid JSON')
+        mock_get.return_value = mock_response
+
+        result = weather_fetcher.get_weather(25.0, 121.0)
+
+        assert result is None
+
+    @patch('hiking_assistant.weather.requests.get')
+    def test_get_weather_api_parameters(self, mock_get, weather_fetcher, mock_weather_response):
+        """Test that correct API parameters are sent."""
+        mock_response = Mock()
+        mock_response.json.return_value = mock_weather_response
+        mock_get.return_value = mock_response
+
+        weather_fetcher.get_weather(25.123, 121.456)
+
+        # Verify the call was made with correct parameters
+        mock_get.assert_called_once()
+        call_args = mock_get.call_args
+        params = call_args[1]['params']
+
+        assert params['latitude'] == 25.123
+        assert params['longitude'] == 121.456
+        assert params['timezone'] == 'auto'
+        assert params['forecast_days'] == 7
+
+    @patch('hiking_assistant.weather.requests.get')
+    def test_get_weather_timeout_parameter(self, mock_get, weather_fetcher, mock_weather_response):
+        """Test that timeout parameter is used."""
+        mock_response = Mock()
+        mock_response.json.return_value = mock_weather_response
+        mock_get.return_value = mock_response
+
+        weather_fetcher.get_weather(25.0, 121.0)
+
+        # Verify timeout was passed
+        call_args = mock_get.call_args
+        assert call_args[1]['timeout'] == 8
+
+
+class TestWeatherFetcherEdgeCases:
+    """Test edge cases for WeatherFetcher."""
+
+    def test_forecast_days_minimum_is_one(self):
+        """Test that forecast_days is at least 1."""
+        from hiking_assistant.weather import WeatherFetcher
+
+        fetcher = WeatherFetcher(forecast_days=0)
+        assert fetcher.forecast_days == 1
+
+        fetcher = WeatherFetcher(forecast_days=-5)
+        assert fetcher.forecast_days == 1
+
+    def test_wind_direction_boundary_values(self):
+        """Test wind direction conversion at boundary values."""
+        from hiking_assistant.weather import WeatherFetcher
+
+        fetcher = WeatherFetcher()
+
+        # Test 360 degrees (same as 0)
+        result_0 = fetcher.convert_wind_degrees_to_flow_direction(0)
+        result_360 = fetcher.convert_wind_degrees_to_flow_direction(360)
+        assert result_0 == result_360
+
+    def test_wind_speed_boundary_values(self):
+        """Test wind speed indicators at exact boundary values."""
+        from hiking_assistant.weather import WeatherFetcher
+
+        fetcher = WeatherFetcher()
+
+        assert fetcher.get_wind_speed_indicator(20) == '🟡'  # Exactly 20
+        assert fetcher.get_wind_speed_indicator(40) == '🟠'  # Exactly 40
+        assert fetcher.get_wind_speed_indicator(60) == '🔴'  # Exactly 60
+
+    def test_uv_index_boundary_values(self):
+        """Test UV index indicators at exact boundary values."""
+        from hiking_assistant.weather import WeatherFetcher
+
+        fetcher = WeatherFetcher()
+
+        assert fetcher.get_uv_index_indicator(2) == '🟢'  # Exactly 2
+        assert fetcher.get_uv_index_indicator(5) == '🟡'  # Exactly 5
+        assert fetcher.get_uv_index_indicator(7) == '🟠'  # Exactly 7
+        assert fetcher.get_uv_index_indicator(10) == '🔴'  # Exactly 10