TransformStreams { public Map<Long, Order> p04_mapOrdersById(Customer customer) { return null; }  List<OrderDto> p01_toDtos(List<Order> orders); Set<PaymentMethod> p02_getUsedPaymentMethods(Customer customer); SortedSet<LocalDate> p03_getOrderDatesAscending(Customer customer); Map<Long, Order> p04_mapOrdersById(Customer customer); Map<PaymentMethod, List<Order>> p05_getProductsByPaymentMethod(Customer customer); Map<Product, Long> p06_getProductCount(Customer customer); List<Product> p07_getAllOrderedProducts(Customer customer); String p08_getProductsJoined(Customer customer); Long p09_getApproximateTotalOrdersPrice(Customer customer); List<OrderLine> p10_readOrderFromFile(File file);  }
@Test public void p04_mapOrdersById() { Order order1 = new Order(1L); Map<Long, Order> actual = service.p04_mapOrdersById(new Customer(order1)); Map<Long, Order> expected = Collections.singletonMap(1L, order1); assertEquals(expected, actual); }