You have orders (order_id, customer_id, total) and a multi-row order_items (order_id, sku). Compute revenue per customer from the order totals.
Each order's total counts exactly once, however many item rows it has. Every order counts, including orders that have no rows in order_items yet.
Return a dict {customer_id: revenue}.
What the tests check
3 on Run · 4 on Submit01revenue is not inflated by the item fan-out
02multiple orders per customer sum correctly
03orders with no item rows still count toward revenue
Submit runs these and one more check you don’t see, so code written for the visible tests alone can still miss.