diff --git a/src/tutorial/testing/shop/pricing.py b/src/tutorial/testing/shop/pricing.py
index 62f2613..608fb4f 100644
--- a/src/tutorial/testing/shop/pricing.py
+++ b/src/tutorial/testing/shop/pricing.py
@@ -1,2 +1,6 @@
 def discount_price(price: float, percent: float) -> float:
+    if price < 0:
+        raise ValueError("Price must be >= 0")
+    if not 0 <= percent <= 100:
+        raise ValueError("Percent must be between 0 and 100")
     return price - price * percent / 100
diff --git a/tests/test_tutorial/shop/test_pricing.py b/tests/test_tutorial/shop/test_pricing.py
index 5062ace..c6071cf 100644
--- a/tests/test_tutorial/shop/test_pricing.py
+++ b/tests/test_tutorial/shop/test_pricing.py
@@ -1,6 +1,21 @@
 from src.tutorial.testing.shop.pricing import discount_price
+import pytest
 
 
 def test_discount_price_reduces_price():
     result = discount_price(100.0, 20.0)
     assert result == 80
+
+    assert discount_price(100.0, 50.0) == 50
+    assert discount_price(100.0, 0) == 100
+    assert discount_price(100.0, 100) == 0
+
+
+def test_negative_orice_raises_value_error() -> None:
+    with pytest.raises(ValueError):
+        discount_price(-100.0, 50.0) is ValueError
+
+
+def test_percent_above_hundered_message() -> None:
+    with pytest.raises(ValueError, match="between 0 and 100"):
+        discount_price(100.0, 150.0)