diff --git a/python/tests/test_gilded_rose.py b/python/tests/test_gilded_rose.py
index 1c92f638..0006ef6e 100644
--- a/python/tests/test_gilded_rose.py
+++ b/python/tests/test_gilded_rose.py
@@ -1,16 +1,193 @@
-# -*- coding: utf-8 -*-
-import unittest
+"""Unit tests for Gilded Rose strategy classes."""
+from __future__ import annotations
 
-from gilded_rose import Item, GildedRose
+from gilded_rose import (
+    AgedBrieStrategy,
+    BackstagePassStrategy,
+    ConjuredItemStrategy,
+    Item,
+    NormalItemStrategy,
+    SulfurasStrategy,
+)
 
 
-class GildedRoseTest(unittest.TestCase):
-    def test_foo(self):
-        items = [Item("foo", 0, 0)]
-        gilded_rose = GildedRose(items)
-        gilded_rose.update_quality()
-        self.assertEqual("fixme", items[0].name)
+class TestNormalItemStrategy:
+    """Tests for normal item degradation."""
 
-        
-if __name__ == '__main__':
-    unittest.main()
+    def test_quality_decreases_by_one_before_sell_date(self) -> None:
+        """Normal items lose 1 quality per day before sell date."""
+        item = Item("+5 Dexterity Vest", sell_in=10, quality=20)
+        strategy = NormalItemStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 19
+
+    def test_quality_decreases_by_two_after_sell_date(self) -> None:
+        """Normal items lose 2 quality per day after sell date."""
+        item = Item("+5 Dexterity Vest", sell_in=0, quality=20)
+        strategy = NormalItemStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 18
+
+    def test_quality_never_negative(self) -> None:
+        """Quality cannot go below zero."""
+        item = Item("+5 Dexterity Vest", sell_in=5, quality=0)
+        strategy = NormalItemStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 0
+
+    def test_sell_in_decreases(self) -> None:
+        """Sell_in decreases by 1 each day."""
+        item = Item("+5 Dexterity Vest", sell_in=10, quality=20)
+        strategy = NormalItemStrategy()
+
+        strategy.update_sell_in(item)
+
+        assert item.sell_in == 9
+
+
+class TestAgedBrieStrategy:
+    """Tests for Aged Brie appreciation."""
+
+    def test_quality_increases_before_sell_date(self) -> None:
+        """Aged Brie gains 1 quality per day before sell date."""
+        item = Item("Aged Brie", sell_in=10, quality=0)
+        strategy = AgedBrieStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 1
+
+    def test_quality_increases_twice_after_sell_date(self) -> None:
+        """Aged Brie gains 2 quality per day after sell date."""
+        item = Item("Aged Brie", sell_in=0, quality=0)
+        strategy = AgedBrieStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 2
+
+    def test_quality_never_exceeds_50(self) -> None:
+        """Quality cannot exceed 50."""
+        item = Item("Aged Brie", sell_in=10, quality=50)
+        strategy = AgedBrieStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 50
+
+    def test_sell_in_decreases(self) -> None:
+        """Sell_in decreases by 1 each day."""
+        item = Item("Aged Brie", sell_in=10, quality=0)
+        strategy = AgedBrieStrategy()
+
+        strategy.update_sell_in(item)
+
+        assert item.sell_in == 9
+
+
+class TestSulfurasStrategy:
+    """Tests for Sulfuras legendary item."""
+
+    def test_quality_never_changes(self) -> None:
+        """Sulfuras quality remains constant at 80."""
+        item = Item("Sulfuras, Hand of Ragnaros", sell_in=0, quality=80)
+        strategy = SulfurasStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 80
+
+    def test_sell_in_never_changes(self) -> None:
+        """Sulfuras never needs to be sold."""
+        item = Item("Sulfuras, Hand of Ragnaros", sell_in=0, quality=80)
+        strategy = SulfurasStrategy()
+
+        strategy.update_sell_in(item)
+
+        assert item.sell_in == 0
+
+
+class TestBackstagePassStrategy:
+    """Tests for Backstage pass appreciation."""
+
+    def test_quality_increases_by_1_when_more_than_10_days(self) -> None:
+        """Backstage pass gains 1 quality when > 10 days remain."""
+        item = Item("Backstage passes to a TAFKAL80ETC concert", sell_in=15, quality=20)
+        strategy = BackstagePassStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 21
+
+    def test_quality_increases_by_2_when_10_days_or_less(self) -> None:
+        """Backstage pass gains 2 quality when 6-10 days remain."""
+        item = Item("Backstage passes to a TAFKAL80ETC concert", sell_in=10, quality=20)
+        strategy = BackstagePassStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 22
+
+    def test_quality_increases_by_3_when_5_days_or_less(self) -> None:
+        """Backstage pass gains 3 quality when 1-5 days remain."""
+        item = Item("Backstage passes to a TAFKAL80ETC concert", sell_in=5, quality=20)
+        strategy = BackstagePassStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 23
+
+    def test_quality_drops_to_zero_after_concert(self) -> None:
+        """Backstage pass becomes worthless after concert."""
+        item = Item("Backstage passes to a TAFKAL80ETC concert", sell_in=0, quality=20)
+        strategy = BackstagePassStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 0
+
+    def test_quality_never_exceeds_50(self) -> None:
+        """Quality cannot exceed 50."""
+        item = Item("Backstage passes to a TAFKAL80ETC concert", sell_in=5, quality=49)
+        strategy = BackstagePassStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 50
+
+
+class TestConjuredItemStrategy:
+    """Tests for Conjured item degradation."""
+
+    def test_quality_decreases_by_two_before_sell_date(self) -> None:
+        """Conjured items lose 2 quality per day before sell date."""
+        item = Item("Conjured Mana Cake", sell_in=10, quality=20)
+        strategy = ConjuredItemStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 18
+
+    def test_quality_decreases_by_four_after_sell_date(self) -> None:
+        """Conjured items lose 4 quality per day after sell date."""
+        item = Item("Conjured Mana Cake", sell_in=-1, quality=20)  # Past sell date
+        strategy = ConjuredItemStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 16
+
+    def test_quality_never_negative(self) -> None:
+        """Quality cannot go below zero."""
+        item = Item("Conjured Mana Cake", sell_in=5, quality=1)
+        strategy = ConjuredItemStrategy()
+
+        strategy.update_quality(item)
+
+        assert item.quality == 0