Harden MCP article and weight workflows

tests/test_roll_calculation.py

@@ -8,6 +8,7 @@ from roll_calculation import (
     CalculationState,
     _canonical_name,
     article_production_site,
+    calculate_material_weight,
     calculate_roll,
     get_article,
     modify_calculation,
@@ -182,6 +183,35 @@ class RollCalculationTests(unittest.TestCase):
         self.assertEqual(result["status"], "success")
         self.assertIsNone(result["calculation"]["roll_weight_kg"])
 
+    def test_material_weight_does_not_require_or_assume_a_core_diameter(self):
+        result = calculate_material_weight(
+            roll_length_m=60,
+            width_m=5.0,
+            area_weight_g_m2=4850.079676,
+        )
+
+        self.assertEqual(result["status"], "success")
+        self.assertEqual(result["weight_scope"], "material_only")
+        self.assertAlmostEqual(result["material_weight_kg"], 1455.0239028)
+        self.assertNotIn("core_diameter_mm", result["inputs"])
+
+    def test_roll_diameter_still_rejects_a_zero_core_diameter(self):
+        result = calculate_roll(
+            {
+                "roll_length_m": 60,
+                "width_m": 5.0,
+                "area_weight_g_m2": 4850.079676,
+                "thickness_mm": 6.461044,
+                "core_diameter_mm": 0,
+                "include_roll_weight": True,
+            }
+        )
+
+        self.assertEqual(result["status"], "invalid_parameter")
+        self.assertIn("core_diameter_mm", [
+            item["field"] for item in result["invalid"]
+        ])
+
     def test_diameter_only_calculation_does_not_require_width(self):
         result = self.calculate_fixture(
             {