Port Round 1 to Python (OrderDomain): 7 tests green, START state preserved

python/tests/order_tests/test_order_total.py

@@ -0,0 +1,77 @@
+from decimal import Decimal
+
+from order_domain import Order
+from order_state import assert_order_state
+
+
+# This test was refactored - notice the custom matcher.
+# The other tests still need the same treatment.
+def test_discount_on_first_line_total_and_line_values():
+    order = Order()
+    order.add_line(Decimal("100"), 2)  # line 0: 200 -> 160 with discount
+    order.add_line(Decimal("50"), 1)  # line 1: 50
+
+    order.apply_discount(0)
+
+    assert_order_state(
+        order, total=Decimal("210"), line_values=[Decimal("160"), Decimal("50")]
+    )
+
+
+def test_discount_on_second_line_total_and_line_values():
+    order = Order()
+    order.add_line(Decimal("100"), 2)  # line 0: 200
+    order.add_line(Decimal("50"), 1)  # line 1: 50 -> 40 with discount
+
+    order.apply_discount(1)
+
+    assert order.total == Decimal("240")
+    assert order.lines[0].value == Decimal("200")
+    assert order.lines[1].value == Decimal("40")
+
+
+def test_discount_on_both_lines_total_and_line_values():
+    order = Order()
+    order.add_line(Decimal("100"), 2)  # line 0: 200 -> 160
+    order.add_line(Decimal("50"), 1)  # line 1: 50 -> 40
+
+    order.apply_discount(0)
+    order.apply_discount(1)
+
+    assert order.total == Decimal("200")
+    assert order.lines[0].value == Decimal("160")
+    assert order.lines[1].value == Decimal("40")
+
+
+def test_no_discount_total_and_line_values():
+    order = Order()
+    order.add_line(Decimal("100"), 2)  # line 0: 200
+    order.add_line(Decimal("50"), 1)  # line 1: 50
+
+    assert order.total == Decimal("250")
+    assert order.lines[0].value == Decimal("200")
+    assert order.lines[1].value == Decimal("50")
+
+
+def test_single_line_with_discount_total_and_value():
+    order = Order()
+    order.add_line(Decimal("75"), 4)  # line 0: 300 -> 240
+
+    order.apply_discount(0)
+
+    assert order.total == Decimal("240")
+    assert order.lines[0].value == Decimal("240")
+
+
+def test_three_lines_one_discount_total_and_line_values():
+    order = Order()
+    order.add_line(Decimal("20"), 1)  # line 0: 20
+    order.add_line(Decimal("30"), 2)  # line 1: 60 -> 48
+    order.add_line(Decimal("10"), 3)  # line 2: 30
+
+    order.apply_discount(1)
+
+    assert order.total == Decimal("98")
+    assert order.lines[0].value == Decimal("20")
+    assert order.lines[1].value == Decimal("48")
+    assert order.lines[2].value == Decimal("30")