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

python/tests/order_tests/order_state.py

@@ -0,0 +1,32 @@
+"""Custom matcher that bundles multiple order assertions into one.
+
+Participants: you do not need to understand how this works —
+just recognize the pattern and use it as an example for the agent.
+"""
+
+from decimal import Decimal
+
+from order_domain import Order
+
+
+def assert_order_state(
+    order: Order, *, total: Decimal, line_values: list[Decimal]
+) -> None:
+    actual_total = order.total
+    actual_line_values = [line.value for line in order.lines]
+
+    details: list[str] = []
+    if actual_total != total:
+        details.append(f"Total: expected {total}, but was {actual_total}")
+    if actual_line_values != line_values:
+        details.append(
+            f"Line values: expected [{', '.join(str(v) for v in line_values)}], "
+            f"but was [{', '.join(str(v) for v in actual_line_values)}]"
+        )
+
+    if details:
+        header = (
+            f"Expected order with total {total} and line values "
+            f"[{', '.join(str(v) for v in line_values)}] but was:"
+        )
+        raise AssertionError("\n".join([header, *details]))