public interface ItemService {
  String getItemNameUpperCase(String itemId);
}

@Service
public class ItemServiceImpl implements ItemService {

  @Resource
  private ItemRepository itemRepository;

  @Override
  public String getItemNameUpperCase(String itemId) {

    Item item = itemRepository.findById(itemId);

    if (item == null) {
      return null;
    }
    return item.getName().toUpperCase();
  }
}

// 測試用例
import org.junit.Before;
import org.junit.Test;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;

import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.Mockito.*;

public class ItemServiceTest {

  @Mock
  private ItemRepository itemRepository;

  @InjectMocks
  private ItemServiceImpl itemService;

  @Before
  public void setUp(){
    MockitoAnnotations.initMocks(this);
  }

  /**
   * 如果從存儲層查詢到一個Item, 那么它的 name 將被轉(zhuǎn)化為大寫.
   */
  @Test
  public void shouldReturnItemNameInUpperCase() {

    // Given
    Item mockedItem = new Item("it1", "Item 1", "This is item 1", 2000, true);
    when(itemRepository.findById("it1")).thenReturn(mockedItem);

    // When
    String result = itemService.getItemNameUpperCase("it1");

    // Then
    verify(itemRepository, times(1)).findById("it1");
    assertThat(result).isEqualTo("ITEM 1");
  }
}