MapStruct映射器测试报错：ParameterResolutionException问题求助

报错信息（中文翻译） #

org.junit.jupiter.api.extension.ParameterResolutionException: 没有为构造函数[public com.asd.mapper.UserToUserDTOMapperTest(com.asd.mapper.UserToUserDTOMapper)]中的参数[final com.asd.mapper.UserToUserDTOMapper mapper]注册参数解析器

问题原因 #

测试类通过@RequiredArgsConstructor尝试注入MapStruct生成的Spring Bean，但JUnit 5默认不会启动Spring容器，无法识别并注入Spring管理的Bean，导致找不到参数解析器。

解决方案 #

方案一：启用Spring测试上下文（适合整合Spring环境的测试）

给测试类添加@SpringBootTest注解，让JUnit启动Spring容器，自动注入MapStruct生成的Bean：

import lombok.RequiredArgsConstructor;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;

import static org.junit.jupiter.api.Assertions.*;

@SpringBootTest
@RequiredArgsConstructor
class UserToUserDTOMapperTest {
    private final UserToUserDTOMapper mapper;

    String NAME = "asd";
    String EMAIL = "asd@gmail.com";

    @Test
    public void testMapUserToUserDTO() {
        User user = User.builder().name(NAME).email(EMAIL).build();
        UserDTO userDTO = mapper.mapUserToUserDTO(user);
        assertNotNull(userDTO);
        assertEquals(NAME, userDTO.getName());
        assertEquals(EMAIL, userDTO.getEmail());
    }
}

方案二：手动实例化MapStruct实现类（轻量测试，仅验证映射逻辑）

MapStruct会自动生成名为UserToUserDTOMapperImpl的实现类，直接手动实例化即可，无需依赖Spring容器：

import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.*;

class UserToUserDTOMapperTest {
    private final UserToUserDTOMapper mapper = new UserToUserDTOMapperImpl();

    String NAME = "asd";
    String EMAIL = "asd@gmail.com";

    @Test
    public void testMapUserToUserDTO() {
        User user = User.builder().name(NAME).email(EMAIL).build();
        UserDTO userDTO = mapper.mapUserToUserDTO(user);
        assertNotNull(userDTO);
        assertEquals(NAME, userDTO.getName());
        assertEquals(EMAIL, userDTO.getEmail());
    }
}

内容的提问来源于stack exchange，提问作者user1379280