Java中如何有效测试包含私有方法的公共方法

// 假设的User实体类 class User {     private String username;     private String password;     private Long id;      public User(String username, String password) {         this.username = username;     }      public User(String username, String password, Long id) {         this.username = username;         this.password = password;         this.id = id;     }      public String getUsername() { return username; }     public Long getId() { return id; }     // ... 其他getter/setter }  // 假设的UserRepository接口 interface UserRepository {     boolean existsByUsername(String username);     User save(User user); }  // 假设的自定义异常 class UsernameUnavailableException extends RuntimeException {     public UsernameUnavailableException(String message) { super(message); } }  class UsernameIsInUseException extends RuntimeException {     public UsernameIsInUseException(String message) { super(message); } }  // 待测试的UserService类 public class UserService {     private final UserRepository userRepository;      public UserService(UserRepository userRepository) {         this.userRepository = userRepository;     }      public User create(User user) {         checkUsername(user.getUsername()); // 公共方法调用私有方法         return userRepository.save(user);     }      private void checkUsername(String username) {         if (username.equals("dummy")) {             String msg = String.format("Username = '%s is cannot be used!", username);             throw new UsernameUnavailableException(msg);         } else if (!userRepository.existsByUsername(username)) {             return; // 用户名可用         }          String msg = String.format("Username ='s%s' is being used by another user!", username);         throw new UsernameIsInUseException(msg);     } }

import org.junit.jupiter.api.BeforeEach; import org.junit.jupiter.api.Test; import org.mockito.InjectMocks; import org.mockito.Mock; import org.mockito.MockitoAnnotations;  import static org.junit.jupiter.api.Assertions.*; import static org.mockito.Mockito.*;  class UserServiceTest {      @Mock // 模拟UserRepository接口     private UserRepository userRepository;      @InjectMocks // 将模拟的userRepository注入到UserService实例中     private UserService userService;      @BeforeEach     void setUp() {         // 初始化所有@Mock和@InjectMocks注解的字段         MockitoAnnotations.openMocks(this);     }      @Test     void create_shouldThrowUsernameUnavailableException_whenUsernameIsDummy() {         User dummyUser = new User("dummy", "password");          // 断言create方法会抛出特定的异常         UsernameUnavailableException exception = assertThrows(UsernameUnavailableException.class, () -> {             userService.create(dummyUser);         });          // 验证异常消息         assertEquals("Username = 'dummy is cannot be used!", exception.getMessage());          // 验证userRepository的任何方法都没有被调用         // 这间接证明了checkUsername在抛出异常前没有与userRepository交互         verifyNoInteractions(userRepository);     }      @Test     void create_shouldThrowUsernameIsInUseException_whenUsernameExists() {         User existingUser = new User("existingUser", "password");         // 模拟当existsByUsername被调用时返回true，表示用户名已存在         when(userRepository.existsByUsername("existingUser")).thenReturn(true);          // 断言create方法会抛出特定的异常         UsernameIsInUseException exception = assertThrows(UsernameIsInUseException.class, () -> {             userService.create(existingUser);         });          // 验证异常消息         assertEquals(String.format("Username ='s%s' is being used by another user!", existingUser.getUsername()), exception.getMessage());          // 验证userRepository.existsByUsername方法被调用了一次         verify(userRepository, times(1)).existsByUsername("existingUser");         // 验证userRepository.save方法从未被调用         verify(userRepository, never()).save(any(User.class));     }      @Test     void create_shouldSaveUserSuccessfully_whenUsernameIsAvailable() {         User newUser = new User("newUser", "password");         User savedUser = new User("newUser", "password", 1L); // 模拟保存后的用户          // 模拟当existsByUsername被调用时返回false，表示用户名可用         when(userRepository.existsByUsername("newUser")).thenReturn(false);         // 模拟当save方法被调用时返回一个已保存的用户对象         when(userRepository.save(any(User.class))).thenReturn(savedUser);          // 调用create方法         User result = userService.create(newUser);          // 断言结果不为空，且与预期保存的用户匹配         assertNotNull(result);         assertEquals(savedUser.getUsername(), result.getUsername());         assertEquals(savedUser.getId(), result.getId());          // 验证userRepository.existsByUsername方法被调用了一次         verify(userRepository, times(1)).existsByUsername("newUser");         // 验证userRepository.save方法被调用了一次，且参数是任何User对象         verify(userRepository, times(1)).save(any(User.class));     } }

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