Order Controller Tests

Write tests for a Spring Boot REST controller that manages food orders. The application has this structure:

• OrderController handles endpoints: POST /api/orders (create), GET /api/orders/{id} (get by id), GET /api/orders (list all)
• OrderService contains business logic and is injected into the controller
• OrderRepository extends JpaRepository<Order, Long>
• Order entity has fields: id, customerName, status, items, total
• Validation: customerName is required (not blank), items must not be empty

Output

Produce a Java test file at src/test/java/com/example/orders/controller/OrderControllerTest.java.

Test at minimum:

1. Creating an order returns 201 with the created order
2. Creating an order with empty customerName returns 400
3. Getting a nonexistent order returns 404
4. Listing orders returns 200 with an array

Do not produce the application source code -- only the test file.