diff --git a/server/src/test/update_average_punctuality/test_update_average_punctuality.py b/server/src/test/update_average_punctuality/test_update_average_punctuality.py
new file mode 100644
index 0000000..141e639
--- /dev/null
+++ b/server/src/test/update_average_punctuality/test_update_average_punctuality.py
@@ -0,0 +1,189 @@
+import unittest
+from unittest.mock import patch, MagicMock
+import json
+from functions.update_average_punctuality.lambda_function import lambda_handler, fetch_train_data, update_punctuality, update_punctuality_by_timestamp
+
+
+class TestPunctualityLambda(unittest.TestCase):
+    """
+    Unit tests for the Lambda function that processes and updates train punctuality data.
+    """
+
+    ### ✅ TEST FETCHING TRAIN DATA ✅ ###
+
+    @patch("functions.update_average_punctuality.lambda_function.requests.get")
+    def test_fetch_train_data_success(self, mock_get):
+        """
+        Test successful train data retrieval from the API.
+        """
+        mock_response = MagicMock()
+        mock_response.status_code = 200
+        mock_response.text = json.dumps([
+            {"objectID": "Train-1", "trainPunctuality": "95", "timestamp": "1711814400"},
+            {"objectID": "Train-2", "trainPunctuality": "88", "timestamp": "1711814400"}
+        ])
+        mock_response.json.return_value = json.loads(mock_response.text)
+
+        mock_get.return_value = mock_response
+
+        result = fetch_train_data()
+        self.assertIsInstance(result, list)
+        self.assertEqual(len(result), 2)
+        self.assertEqual(result[0]["objectID"], "Train-1")
+        self.assertEqual(result[1]["trainPunctuality"], "88")
+
+    @patch("functions.update_average_punctuality.lambda_function.requests.get")
+    def test_fetch_train_data_api_failure(self, mock_get):
+        """
+        Test API failure handling (request error).
+        """
+        mock_get.side_effect = Exception("API request failed")
+
+        with self.assertRaises(Exception) as context:
+            fetch_train_data()
+
+        self.assertEqual(str(context.exception), "API request failed")
+
+    @patch("functions.update_average_punctuality.lambda_function.requests.get")
+    def test_fetch_train_data_empty_response(self, mock_get):
+        """
+        Test handling of empty API response.
+        """
+        mock_response = MagicMock()
+        mock_response.status_code = 200
+        mock_response.text = ""
+        mock_response.json.return_value = []
+
+        mock_get.return_value = mock_response
+
+        result = fetch_train_data()
+        self.assertEqual(result, [])
+
+    @patch("functions.update_average_punctuality.lambda_function.requests.get")
+    def test_fetch_train_data_invalid_json(self, mock_get):
+        """
+        Test handling of invalid JSON response.
+        """
+        mock_response = MagicMock()
+        mock_response.status_code = 200
+        mock_response.text = "invalid json"
+        mock_response.json.side_effect = json.JSONDecodeError("Invalid JSON", doc="", pos=0)
+
+        mock_get.return_value = mock_response
+
+        result = fetch_train_data()
+        self.assertEqual(result, [])
+
+
+    ### ✅ TEST PUNCTUALITY UPDATES IN DYNAMODB ✅ ###
+
+    @patch("functions.update_average_punctuality.lambda_function.table_train.get_item")
+    @patch("functions.update_average_punctuality.lambda_function.table_train.update_item")
+    @patch("functions.update_average_punctuality.lambda_function.table_train.put_item")
+    def test_update_punctuality_existing_train(self, mock_put, mock_update, mock_get):
+        """
+        Test updating punctuality for an existing train record.
+        """
+        mock_get.return_value = {"Item": {"objectID": "Train-1", "average_punctuality": "90", "count": 2}}
+
+        update_punctuality("Train-1", 95)
+
+        mock_update.assert_called_once()
+        mock_put.assert_not_called()
+
+    @patch("functions.update_average_punctuality.lambda_function.table_train.get_item")
+    @patch("functions.update_average_punctuality.lambda_function.table_train.update_item")
+    @patch("functions.update_average_punctuality.lambda_function.table_train.put_item")
+    def test_update_punctuality_new_train(self, mock_put, mock_update, mock_get):
+        """
+        Test inserting a new train punctuality record when the train does not exist.
+        """
+        mock_get.return_value = {}  # No existing record
+
+        update_punctuality("Train-2", 88)
+
+        mock_put.assert_called_once()
+        mock_update.assert_not_called()
+
+    @patch("functions.update_average_punctuality.lambda_function.table_timestamp.put_item")
+    def test_update_punctuality_by_timestamp(self, mock_put):
+        """
+        Test updating punctuality by timestamp.
+        """
+        update_punctuality_by_timestamp(1711814400, [90, 85, 80])
+
+        mock_put.assert_called_once()
+
+
+    ### ✅ TEST LAMBDA HANDLER EXECUTION ✅ ###
+
+    @patch("functions.update_average_punctuality.lambda_function.fetch_train_data")
+    @patch("functions.update_average_punctuality.lambda_function.update_punctuality")
+    @patch("functions.update_average_punctuality.lambda_function.update_punctuality_by_timestamp")
+    def test_lambda_handler_success(self, mock_update_by_timestamp, mock_update_punctuality, mock_fetch_data):
+        """
+        Test successful execution of the lambda handler.
+        """
+        mock_fetch_data.return_value = [
+            {"objectID": "Train-1", "trainPunctuality": "95", "timestamp": "1711814400"},
+            {"objectID": "Train-2", "trainPunctuality": "88", "timestamp": "1711814400"}
+        ]
+
+        event = {}
+        result = lambda_handler(event, {})
+
+        self.assertEqual(result["statusCode"], 200)
+        self.assertIn("Punctuality data updated successfully", result["body"])
+        mock_update_punctuality.assert_called()
+        mock_update_by_timestamp.assert_called_once()
+
+    @patch("functions.update_average_punctuality.lambda_function.fetch_train_data")
+    def test_lambda_handler_no_data(self, mock_fetch_data):
+        """
+        Test lambda handler when no train data is available.
+        """
+        mock_fetch_data.return_value = []
+
+        event = {}
+        result = lambda_handler(event, {})
+
+        self.assertEqual(result["statusCode"], 500)
+        self.assertIn("No train data available", result["body"])
+
+    @patch("functions.update_average_punctuality.lambda_function.fetch_train_data")
+    def test_lambda_handler_missing_timestamp(self, mock_fetch_data):
+        """
+        Test lambda handler when train data is missing timestamps.
+        """
+        mock_fetch_data.return_value = [
+            {"objectID": "Train-1", "trainPunctuality": "95"}
+        ]
+
+        event = {}
+        result = lambda_handler(event, {})
+
+        self.assertEqual(result["statusCode"], 500)
+        self.assertIn("Missing timestamp in train data", result["body"])
+
+    @patch("functions.update_average_punctuality.lambda_function.fetch_train_data")
+    @patch("functions.update_average_punctuality.lambda_function.update_punctuality")
+    @patch("functions.update_average_punctuality.lambda_function.update_punctuality_by_timestamp")
+    def test_lambda_handler_single_train_entry(self, mock_update_by_timestamp, mock_update_punctuality, mock_fetch_data):
+        """
+        Test lambda handler with a single train data entry.
+        """
+        mock_fetch_data.return_value = [
+            {"objectID": "Train-1", "trainPunctuality": "90", "timestamp": "1711814400"}
+        ]
+
+        event = {}
+        result = lambda_handler(event, {})
+
+        self.assertEqual(result["statusCode"], 200)
+        self.assertIn("Punctuality data updated successfully", result["body"])
+        mock_update_punctuality.assert_called_once()
+        mock_update_by_timestamp.assert_called_once()
+
+
+if __name__ == "__main__":
+    unittest.main()