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

python/tests/order_tests/test_order_completion.py

@@ -0,0 +1,11 @@
+from decimal import Decimal
+
+from order_domain import Order
+
+
+def test_completed_order_total_is_correct():
+    order = Order()
+    order.add_line(Decimal("100"), 1)
+    order.complete()
+
+    assert order.is_fully_paid(Decimal("100"))