Port Round 2 to Python (OrderBook): 14 tests total green, START state preserved

python/tests/order_book_tests/test_order_book_lifecycle.py

@@ -0,0 +1,104 @@
+from datetime import datetime, timedelta, timezone
+
+import pytest
+
+from order_book_domain import OrderBook, OrderStatus
+
+DAY0 = datetime(2025, 6, 1, tzinfo=timezone.utc)
+
+
+def at(day: int) -> datetime:
+    return DAY0 + timedelta(days=day)
+
+
+def test_finalize_then_pay_moves_order_through_two_states():
+    book = OrderBook()
+    order = book.open_order("anna")
+
+    book.finalize_order(order.id, at(1))
+    assert book.get_order(order.id).status is OrderStatus.WAITING_FOR_PAYMENT
+
+    book.pay_order(order.id, at(2))
+    assert book.get_order(order.id).status is OrderStatus.FULFILLING
+
+
+def test_pay_then_ship_delivers_the_order():
+    book = OrderBook()
+    order = book.open_order("anna")
+
+    book.finalize_order(order.id, at(1))
+    assert book.get_order(order.id).status is OrderStatus.WAITING_FOR_PAYMENT
+
+    book.pay_order(order.id, at(2))
+    book.ship_order(order.id)
+    assert book.get_order(order.id).status is OrderStatus.DELIVERED
+
+
+def test_pay_within_window_then_late_pay_on_second_order_cancels_only_that_order():
+    book = OrderBook()
+    first = book.open_order("anna")
+    second = book.open_order("bram")
+
+    book.finalize_order(first.id, at(1))
+    book.finalize_order(second.id, at(1))
+    assert len(book.orders) == 2
+
+    book.pay_order(first.id, at(5))
+    assert book.get_order(first.id).status is OrderStatus.FULFILLING
+
+    with pytest.raises(ValueError):
+        book.pay_order(second.id, at(30))
+    assert book.get_order(second.id).status is OrderStatus.CANCELLED
+
+
+def test_pay_before_finalize_throws_then_finalize_still_works():
+    book = OrderBook()
+    order = book.open_order("anna")
+
+    with pytest.raises(ValueError):
+        book.pay_order(order.id, at(1))
+    assert book.get_order(order.id).status is OrderStatus.PENDING
+
+    book.finalize_order(order.id, at(2))
+    assert book.get_order(order.id).status is OrderStatus.WAITING_FOR_PAYMENT
+
+
+def test_cancel_pending_order_then_pay_after_cancel_throws_again():
+    book = OrderBook()
+    order = book.open_order("anna")
+
+    book.cancel_order(order.id)
+    assert book.get_order(order.id).status is OrderStatus.CANCELLED
+
+    with pytest.raises(ValueError):
+        book.pay_order(order.id, at(1))
+    assert book.get_order(order.id).status is OrderStatus.CANCELLED
+
+
+def test_shipped_order_cannot_be_cancelled():
+    book = OrderBook()
+    order = book.open_order("anna")
+
+    book.finalize_order(order.id, at(1))
+    book.pay_order(order.id, at(2))
+    book.ship_order(order.id)
+    assert book.get_order(order.id).status is OrderStatus.DELIVERED
+
+    with pytest.raises(ValueError):
+        book.cancel_order(order.id)
+    assert book.get_order(order.id).status is OrderStatus.DELIVERED
+
+
+def test_two_customers_interleave_transitions_independently():
+    book = OrderBook()
+    annas = book.open_order("anna")
+    brams = book.open_order("bram")
+
+    book.finalize_order(brams.id, at(1))
+    assert book.get_order(annas.id).status is OrderStatus.PENDING
+    assert book.get_order(brams.id).status is OrderStatus.WAITING_FOR_PAYMENT
+
+    book.pay_order(brams.id, at(2))
+    book.cancel_order(annas.id)
+    assert book.get_order(annas.id).status is OrderStatus.CANCELLED
+    assert book.get_order(brams.id).status is OrderStatus.FULFILLING