feat: add addition and subtraction to Money and Price

domain/marketplace/money.py

@@ -5,3 +5,9 @@ from decimal import Decimal
 @dataclass(frozen=True)
 class Money:
     amount: Decimal
+
+    def __add__(self, other):
+        return Money(self.amount + other.amount)
+
+    def __sub__(self, other):
+        return Money(self.amount - other.amount)

tests/test_money.py

@@ -22,3 +22,18 @@ def test_money_equality():
     money1 = Money(amount=Decimal("50.00"))
     money2 = Money(amount=Decimal("50.00"))
     assert money1 == money2
+
+
+def test_money_add():
+    money1 = Money(amount=Decimal("2.00"))
+    money2 = Money(amount=Decimal("3.00"))
+
+    assert (money1 + money2) == Money(amount=Decimal("5.00"))
+    assert money1 == Money(amount=Decimal("2.00"))
+    assert money2 == Money(amount=Decimal("3.00"))
+
+
+def test_money_substract():
+    money1 = Money(amount=Decimal("5.00"))
+    money2 = Money(amount=Decimal("3.00"))
+    assert (money1 - money2) == Money(amount=Decimal("2.00"))