Harden MCP tool composition

tests/test_roll_calculation.py

@@ -10,6 +10,7 @@ from roll_calculation import (
     calculate_roll,
     get_article,
     modify_calculation,
+    transport_roll_inputs_from_roll_calculation,
 )
 
 
@@ -131,6 +132,48 @@ class RollCalculationTests(unittest.TestCase):
         self.assertEqual(calculation["effective_roll_length_m"], 50.0)
         self.assertAlmostEqual(calculation["roll_weight_kg"], 512.4909)
 
+    def test_transport_roll_inputs_match_browser_average_and_display_rounding(self):
+        result = calculate_roll(representative_request())
+
+        self.assertEqual(
+            transport_roll_inputs_from_roll_calculation(result),
+            {
+                "roll_diameter_mm": 845.9,
+                "core_diameter_mm": 150.0,
+                "roll_width_m": 5.8,
+                "roll_weight_kg": 512.5,
+                "product_length_m": 50.0,
+            },
+        )
+
+    def test_transport_roll_inputs_use_browser_equivalent_half_rounding(self):
+        result = {
+            "status": "success",
+            "calculation": {
+                "average_diameter_mm": 1000.25,
+                "roll_weight_kg": 12.25,
+                "effective_roll_length_m": 10.0,
+            },
+            "effective_inputs": {
+                "core_diameter_mm": {"value": 150.0},
+                "width_m": {"value": 2.0},
+            },
+        }
+
+        inputs = transport_roll_inputs_from_roll_calculation(result)
+
+        self.assertEqual(inputs["roll_diameter_mm"], 1000.3)
+        self.assertEqual(inputs["roll_weight_kg"], 12.3)
+
+    def test_transport_roll_inputs_reject_unsuccessful_or_incomplete_results(self):
+        for result in (
+            {"status": "needs_clarification"},
+            {"status": "success", "calculation": {}, "effective_inputs": {}},
+        ):
+            with self.subTest(result=result):
+                with self.assertRaises(ValueError):
+                    transport_roll_inputs_from_roll_calculation(result)
+
     def test_optional_weight_is_omitted_without_requesting_it(self):
         result = calculate_roll(
             representative_request(width_m=None, include_roll_weight=False)