Switch to decimal.Decimal for money

Floating point data types are not suitable to represent money since
rounding issues will sum up.

2 files changed, 10 insertions, 8 deletions

diff --git a/finance/income.py b/finance/income.py
index 94759ff..8d775cb 100644
--- a/finance/income.py
+++ b/finance/income.py
@@ -1,17 +1,18 @@
 import dataclasses
 from datetime import datetime
+from decimal import Decimal
 
 
 @dataclasses.dataclass(kw_only=True, frozen=True)
 class Income:
     """Income models financial income paid on the first day of a month"""
 
-    amount: float
+    amount: Decimal
 
-    def integrate(self, start: datetime, end: datetime) -> float:
+    def integrate(self, start: datetime, end: datetime) -> Decimal:
         """Integrate the income from a start to an end date"""
 
-        retval = 0.0
+        retval = Decimal(0.0)
 
         current = datetime(start.year, start.month, 1)
 
diff --git a/finance/test_income.py b/finance/test_income.py
index 0ce3507..fc75bef 100644
--- a/finance/test_income.py
+++ b/finance/test_income.py
@@ -1,16 +1,17 @@
 from datetime import datetime
+from decimal import Decimal
 
 from finance import income
 
 
 def test_income_integration() -> None:
-    inc = income.Income(amount=3000.0)
+    inc = income.Income(amount=Decimal(3000.0))
 
     tests = (
-        (datetime(2024, 3, 12), datetime(2024, 4, 2), 3000.0),
-        (datetime(2024, 3, 1), datetime(2024, 3, 15), 3000.0),
-        (datetime(2024, 2, 25), datetime(2024, 3, 1), 3000.0),
-        (datetime(2024, 2, 25), datetime(2024, 6, 12), 12000.0),
+        (datetime(2024, 3, 12), datetime(2024, 4, 2), Decimal(3000.0)),
+        (datetime(2024, 3, 1), datetime(2024, 3, 15), Decimal(3000.0)),
+        (datetime(2024, 2, 25), datetime(2024, 3, 1), Decimal(3000.0)),
+        (datetime(2024, 2, 25), datetime(2024, 6, 12), Decimal(12000.0)),
     )
 
     for test in tests: