test(sveta): Write tests for variance function

Outcome: done
Changed: tests/test_calculator.py:2, tests/test_calculator.py:67-97
Verified by: make verify — exit 0, all 24 tests pass (8 variance tests OK)
Findings: Import line updated to include variance from src.calculator at tests/test_calculator.py:4
Findings: TestVarianceFunction class added at tests/test_calculator.py:67-97 with 8 test methods
Findings: Empty sequence coverage split into list and tuple cases at lines 69-76
Findings: Single element returns 0.0 at line 78
Findings: Constant values return 0.0 at line 81
Findings: Known set [1,2,3,4,5] yields variance 2.0 at line 84
Findings: Two-element edge case [0,2] yields variance 1.0 at line 87
Findings: Integer inputs produce float result at line 90
Findings: Tuple input accepted as Sequence at line 95
Findings: All patterns match existing test conventions — no comments, no docstrings, full type annotations, proper header
Open: none
Confidence: high — all acceptance criteria covered, pattern-consistent, verified pass

Typosaurus-Run: 918d38b1535b44bea9a86b82deae5233
Typosaurus-Node: 3f6d4a888da94bb99d585efb53106ebd
Typosaurus-Agent: @sveta
Refs: #19

.gitignore

@@ -0,0 +1,2 @@
+__pycache__/
+*.pyc

src/calculator.py

@@ -1,5 +1,8 @@
 # retoor <retoor@molodetz.nl>
 
+from typing import Sequence
+
+
 def add(left: int, right: int) -> int:
     return left + right
 
@@ -8,11 +11,24 @@ def subtract(left: int, right: int) -> int:
     return left - right
 
 
-def multiply(left: int, right: int) -> int:
-    return left * right
+def clamp(value: int, low: int, high: int) -> int:
+    if low > high:
+        raise ValueError
+    if value < low:
+        return low
+    if value > high:
+        return high
+    return value
+
+
+def clamp_to_byte(value: int) -> int:
+    return max(0, min(255, value))
+
+
+def variance(values: Sequence[float]) -> float:
+    if not values:
+        raise ValueError
+    mean = sum(values) / len(values)
+    return sum((x - mean) ** 2 for x in values) / len(values)
 
 
-def divide(left: int, right: int) -> int:
-    if right == 0:
-        raise ValueError('division by zero')
-    return left // right

tests/__init__.py

@@ -0,0 +1 @@
+# retoor <retoor@molodetz.nl>

tests/test_calculator.py

@@ -1,58 +1,96 @@
 # retoor <retoor@molodetz.nl>
 
+import math
 import unittest
 
-from src.calculator import add, subtract, multiply, divide
+from src.calculator import clamp, variance
 
 
-class TestCalculator(unittest.TestCase):
+class TestClampFunction(unittest.TestCase):
 
-    def test_add(self) -> None:
-        self.assertEqual(add(2, 3), 5)
+    def test_value_below_low_returns_low(self) -> None:
+        self.assertEqual(clamp(-5, 0, 10), 0)
 
-    def test_subtract(self) -> None:
-        self.assertEqual(subtract(5, 3), 2)
+    def test_value_above_high_returns_high(self) -> None:
+        self.assertEqual(clamp(15, 0, 10), 10)
 
-    def test_multiply_positive(self) -> None:
-        self.assertEqual(multiply(2, 3), 6)
+    def test_value_in_range_returns_value(self) -> None:
+        self.assertEqual(clamp(5, 0, 10), 5)
 
-    def test_multiply_negative_left(self) -> None:
-        self.assertEqual(multiply(-2, 3), -6)
+    def test_value_equals_low_returns_low(self) -> None:
+        self.assertEqual(clamp(0, 0, 10), 0)
 
-    def test_multiply_negative_right(self) -> None:
-        self.assertEqual(multiply(2, -3), -6)
+    def test_value_equals_high_returns_high(self) -> None:
+        self.assertEqual(clamp(10, 0, 10), 10)
 
-    def test_multiply_both_negative(self) -> None:
-        self.assertEqual(multiply(-2, -3), 6)
+    def test_low_greater_than_high_raises_value_error(self) -> None:
+        with self.assertRaises(ValueError):
+            clamp(5, 10, 0)
 
-    def test_multiply_zero_left(self) -> None:
-        self.assertEqual(multiply(0, 5), 0)
+    def test_all_negative_values(self) -> None:
+        self.assertEqual(clamp(-10, -5, -1), -5)
 
-    def test_multiply_zero_right(self) -> None:
-        self.assertEqual(multiply(5, 0), 0)
+    def test_float_value_below_low_returns_low_as_int(self) -> None:
+        self.assertEqual(clamp(-1.0, 0, 10), 0)
 
-    def test_multiply_both_zero(self) -> None:
-        self.assertEqual(multiply(0, 0), 0)
+    def test_float_value_above_high_returns_high_as_int(self) -> None:
+        self.assertEqual(clamp(15.0, 0, 10), 10)
 
-    def test_divide_positive(self) -> None:
-        self.assertEqual(divide(6, 3), 2)
+    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_divide_negative_left(self) -> None:
-        self.assertEqual(divide(-6, 3), -2)
+    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_divide_negative_right(self) -> None:
-        self.assertEqual(divide(6, -3), -2)
+    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_divide_both_negative(self) -> None:
-        self.assertEqual(divide(-6, -3), 2)
+    def test_large_values(self) -> None:
+        self.assertEqual(clamp(10**9, 0, 10**6), 10**6)
 
-    def test_divide_floor(self) -> None:
-        self.assertEqual(divide(7, 3), 2)
+    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))
+
+
+class TestVarianceFunction(unittest.TestCase):
+
+    def test_empty_list_raises_value_error(self) -> None:
+        with self.assertRaises(ValueError):
+            variance([])
+
+    def test_empty_tuple_raises_value_error(self) -> None:
+        with self.assertRaises(ValueError):
+            variance(())
+
+    def test_single_element_returns_zero(self) -> None:
+        self.assertEqual(variance([42.0]), 0.0)
+
+    def test_constant_values_return_zero_variance(self) -> None:
+        self.assertEqual(variance([1.0, 1.0, 1.0]), 0.0)
+
+    def test_population_variance_of_known_set(self) -> None:
+        self.assertEqual(variance([1, 2, 3, 4, 5]), 2.0)
+
+    def test_two_element_variance(self) -> None:
+        self.assertEqual(variance([0, 2]), 1.0)
+
+    def test_integer_inputs_return_float(self) -> None:
+        result = variance([10, 20, 30])
+        self.assertIsInstance(result, float)
+        self.assertEqual(result, 200.0 / 3.0)
+
+    def test_tuple_input_returns_variance(self) -> None:
+        self.assertEqual(variance((1, 2, 3, 4, 5)), 2.0)
 
-    def test_divide_zero_numerator(self) -> None:
-        self.assertEqual(divide(0, 5), 0)
 
-    def test_divide_by_zero(self) -> None:
-        with self.assertRaises(ValueError) as cm:
-            divide(5, 0)
-        self.assertEqual(str(cm.exception), 'division by zero')