feat: add SulfurasStrategy

python/gilded_rose.py

@@ -71,6 +71,18 @@ class BackstagePassStrategy:
             item.sell_in -= 1
 
 
+class SulfurasStrategy:
+    """
+    No-op strategy for Sulfuras, Hand of Ragnaros.
+
+    Legendary items never degrade and never need to be sold.
+    Neither quality nor sell_in is ever mutated.
+    """
+
+    def update(self, item: "Item", days: int) -> None:
+        pass  # legendary items are immutable; parameters required by Protocol
+
+
 class GildedRose(object):
 
     def __init__(self, items):

python/tests/test_gilded_rose.py

@@ -9,7 +9,7 @@ if str(_EXERCISE_ROOT) not in sys.path:
 
 from gilded_rose import (
     Item, GildedRose, NormalStrategy, AgedBrieStrategy,
-    BackstagePassStrategy,
+    BackstagePassStrategy, SulfurasStrategy,
 )
 
 
@@ -146,5 +146,28 @@ class TestBackstagePassStrategy(unittest.TestCase):
         self.assertEqual(8, item.sell_in)
 
 
+class TestSulfurasStrategy(unittest.TestCase):
+    """Tests for SulfurasStrategy — legendary item, never changes."""
+
+    def setUp(self):
+        self.strategy = SulfurasStrategy()
+
+    def test_quality_never_changes(self):
+        item = Item("Sulfuras, Hand of Ragnaros", sell_in=0, quality=80)
+        self.strategy.update(item, days=1)
+        self.assertEqual(80, item.quality)
+
+    def test_sell_in_never_changes(self):
+        item = Item("Sulfuras, Hand of Ragnaros", sell_in=0, quality=80)
+        self.strategy.update(item, days=1)
+        self.assertEqual(0, item.sell_in)
+
+    def test_unchanged_after_many_days(self):
+        item = Item("Sulfuras, Hand of Ragnaros", sell_in=0, quality=80)
+        self.strategy.update(item, days=100)
+        self.assertEqual(80, item.quality)
+        self.assertEqual(0, item.sell_in)
+
+
 if __name__ == '__main__':
     unittest.main()