diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..95ee7c3
--- /dev/null
+++ b/tests/__init__.py
@@ -0,0 +1 @@
+# retoor <retoor@molodetz.nl>
diff --git a/tests/test_calculator.py b/tests/test_calculator.py
new file mode 100644
index 0000000..48d48d4
--- /dev/null
+++ b/tests/test_calculator.py
@@ -0,0 +1,63 @@
+# retoor <retoor@molodetz.nl>
+
+import math
+import unittest
+
+from src.calculator import clamp
+
+
+class TestClampFunction(unittest.TestCase):
+
+    def test_value_below_low_returns_low(self) -> None:
+        self.assertEqual(clamp(-5, 0, 10), 0)
+
+    def test_value_above_high_returns_high(self) -> None:
+        self.assertEqual(clamp(15, 0, 10), 10)
+
+    def test_value_in_range_returns_value(self) -> None:
+        self.assertEqual(clamp(5, 0, 10), 5)
+
+    def test_value_equals_low_returns_low(self) -> None:
+        self.assertEqual(clamp(0, 0, 10), 0)
+
+    def test_value_equals_high_returns_high(self) -> None:
+        self.assertEqual(clamp(10, 0, 10), 10)
+
+    def test_low_greater_than_high_raises_value_error(self) -> None:
+        with self.assertRaises(ValueError):
+            clamp(5, 10, 0)
+
+    def test_all_negative_values(self) -> None:
+        self.assertEqual(clamp(-10, -5, -1), -5)
+
+    def test_float_value_below_low_returns_low_as_int(self) -> None:
+        self.assertEqual(clamp(-1.0, 0, 10), 0)
+
+    def test_float_value_above_high_returns_high_as_int(self) -> None:
+        self.assertEqual(clamp(15.0, 0, 10), 10)
+
+    def test_float_value_in_range_returns_float(self) -> None:
+        result = clamp(5.0, 0, 10)
+        self.assertIsInstance(result, float)
+        self.assertEqual(result, 5.0)
+
+    def test_float_value_equals_boundary_returns_boundary(self) -> None:
+        self.assertEqual(clamp(0.0, 0, 10), 0)
+        self.assertEqual(clamp(10.0, 0, 10), 10)
+
+    def test_float_low_greater_than_float_high_raises_value_error(self) -> None:
+        with self.assertRaises(ValueError):
+            clamp(5.0, 10.0, 0.0)
+
+    def test_large_values(self) -> None:
+        self.assertEqual(clamp(10**9, 0, 10**6), 10**6)
+
+    def test_negative_infinity_not_clamped_by_default(self) -> None:
+        self.assertEqual(clamp(-math.inf, 0, 10), 0)
+
+    def test_positive_infinity_not_clamped_by_default(self) -> None:
+        self.assertEqual(clamp(math.inf, 0, 10), 10)
+
+    def test_nan_returns_nan(self) -> None:
+        result = clamp(math.nan, 0, 10)
+        self.assertTrue(math.isnan(result))