1. Add Comprehensive Test Cases to cover all existing functionality before making any changes.

python/test_gilded_rose.py

@@ -5,12 +5,112 @@ from gilded_rose import Item, GildedRose
 
 
 class GildedRoseTest(unittest.TestCase):
+    def test_normal_item_before_sell_date(self):
+        items = [Item("Normal Item", 5, 10)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(4, items[0].sell_in)
+        self.assertEqual(9, items[0].quality)
+
+    def test_normal_item_after_sell_date(self):
+        items = [Item("Normal Item", 0, 10)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(-1, items[0].sell_in)
+        self.assertEqual(8, items[0].quality)
+
+    def test_normal_item_quality_never_negative(self):
+        items = [Item("Normal Item", 5, 0)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(4, items[0].sell_in)
+        self.assertEqual(0, items[0].quality)
+
+    # Aged Brie
+    def test_aged_brie_before_sell_date(self):
+        items = [Item("Aged Brie", 5, 10)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(4, items[0].sell_in)
+        self.assertEqual(11, items[0].quality)
+
+    def test_aged_brie_after_sell_date(self):
+        items = [Item("Aged Brie", 0, 10)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(-1, items[0].sell_in)
+        self.assertEqual(12, items[0].quality)
+
+    def test_aged_brie_quality_never_exceeds_50(self):
+        items = [Item("Aged Brie", 5, 50)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(4, items[0].sell_in)
+        self.assertEqual(50, items[0].quality)
+
+    # Sulfuras
+    def test_sulfuras_never_changes(self):
+        items = [Item("Sulfuras, Hand of Ragnaros", 5, 80)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(5, items[0].sell_in)
+        self.assertEqual(80, items[0].quality)
+
+    def test_sulfuras_after_sell_date(self):
+        items = [Item("Sulfuras, Hand of Ragnaros", -1, 80)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(-1, items[0].sell_in)
+        self.assertEqual(80, items[0].quality)
+
+    # Backstage Passes
+    def test_backstage_pass_more_than_10_days(self):
+        items = [Item("Backstage passes to a TAFKAL80ETC concert", 15, 10)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(14, items[0].sell_in)
+        self.assertEqual(11, items[0].quality)
+
+    def test_backstage_pass_10_days_or_less(self):
+        items = [Item("Backstage passes to a TAFKAL80ETC concert", 10, 10)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(9, items[0].sell_in)
+        self.assertEqual(12, items[0].quality)
+
+    def test_backstage_pass_5_days_or_less(self):
+        items = [Item("Backstage passes to a TAFKAL80ETC concert", 5, 10)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(4, items[0].sell_in)
+        self.assertEqual(13, items[0].quality)
+
+    def test_backstage_pass_after_concert(self):
+        items = [Item("Backstage passes to a TAFKAL80ETC concert", 0, 10)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(-1, items[0].sell_in)
+        self.assertEqual(0, items[0].quality)
+
+
+    # Edge Cases
+    def test_unknown_item_type(self):
+        items = [Item("Random Junk", 5, 10)]
+        gilded_rose = GildedRose(items)
+        gilded_rose.update_quality()
+        self.assertEqual(4, items[0].sell_in)
+        self.assertEqual(9, items[0].quality)
+
     def test_foo(self):
         items = [Item("foo", 0, 0)]
         gilded_rose = GildedRose(items)
         gilded_rose.update_quality()
-        self.assertEqual("fixme", items[0].name)
+        self.assertEqual("foo", items[0].name)
+
+
+
+
+
 
-        
 if __name__ == '__main__':
-    unittest.main()
+    unittest.main()