diff --git a/tests/test_calculator.py b/tests/test_calculator.py
index 48d48d4..7583271 100644
--- a/tests/test_calculator.py
+++ b/tests/test_calculator.py
@@ -3,7 +3,7 @@
 import math
 import unittest
 
-from src.calculator import clamp
+from src.calculator import average, clamp
 
 
 class TestClampFunction(unittest.TestCase):
@@ -61,3 +61,25 @@ class TestClampFunction(unittest.TestCase):
     def test_nan_returns_nan(self) -> None:
         result = clamp(math.nan, 0, 10)
         self.assertTrue(math.isnan(result))
+
+
+class TestAverageFunction(unittest.TestCase):
+
+    def test_empty_sequence_raises_value_error(self) -> None:
+        with self.assertRaises(ValueError):
+            average([])
+
+    def test_single_element(self) -> None:
+        self.assertEqual(average([5]), 5.0)
+
+    def test_positive_values(self) -> None:
+        self.assertEqual(average([1, 2, 3, 4, 5]), 3.0)
+
+    def test_negative_values(self) -> None:
+        self.assertEqual(average([-10, -20, -30]), -20.0)
+
+    def test_mixed_positive_and_negative(self) -> None:
+        self.assertEqual(average([-5, 0, 5]), 0.0)
+
+    def test_float_values(self) -> None:
+        self.assertEqual(average([1.5, 2.5, 3.0]), 7.0 / 3.0)