Mockito测试报错：非空参数为null，如何注入ArchiveService字段？

相关代码 #

ArchiveService 实现 #

@Service
class ArchiveService(
        val fnaReactiveClient: FNAReactiveClient,
        val resolvedTopicPrefix: String)

CoreKafkaConfig 配置类 #

@Configuration
@EnableAspectJAutoProxy(proxyTargetClass = true)
class CoreKafkaConfig {
    
    @Value("\${kafka.topicPrefix:}")
    lateinit var topicPrefix: String

    @Bean
    fun resolvedTopicPrefix() = run {
        KafkaTopicsUtil.resolveTopicPrefix(topicPrefix)
    }
}

测试类 ArchiveServiceTest #

@ExtendWith(MockitoExtension::class)
class ArchiveServiceTest {

    @InjectMocks
    lateinit var archiveService: ArchiveService

    @Mock
    lateinit var fnaReactiveClient: FNAReactiveClient

    
 @Test
    fun `create archive with duplicate filenames`() {
        val user = "user"
      
// ... some when and given block ....

        val newDocVer = archiveService.archiveDoc("integration", null, req, ecmHeaders, EcmServiceAsyncConfig.MethodType.ARCHIVE)
       assertEquals(newId, newDocVer)
       
// ... some verify block ....
        }
    }

抛出异常 #

Cannot instantiate @InjectMocks field named 'archiveService' of type 'class tu.xxxx.ecm.services.service.ArchiveService'.
You haven't provided the instance at field declaration so I tried to construct the instance.
However the constructor or the initialization block threw an exception : Parameter specified as non-null is null: method tu.xxx.ecm.services.service.ArchiveService., parameter resolvedTopicPrefix

请问哪里操作错误了？

问题出在测试类中：你仅为ArchiveService的第一个构造参数fnaReactiveClient添加了@Mock注解，但第二个非空参数resolvedTopicPrefix（字符串类型）没有提供任何实例。Mockito自动构造ArchiveService时，无法生成该字符串参数的实例，导致因为非空参数为null而抛出异常。

有两种解决方式：

• 方法一：手动提供字符串参数
  在测试类中添加resolvedTopicPrefix的实例，Mockito会自动将其注入到构造参数中：

  @ExtendWith(MockitoExtension::class)
  class ArchiveServiceTest {
  
      @InjectMocks
      lateinit var archiveService: ArchiveService
  
      @Mock
      lateinit var fnaReactiveClient: FNAReactiveClient
      
      // 添加该字段，值可根据测试场景自定义
      private val resolvedTopicPrefix = "test-topic-prefix"
  }
  

• 方法二：加载Spring测试上下文
  如果需要贴近真实运行环境，可改用@SpringBootTest启动Spring上下文，配合@MockBean替换fnaReactiveClient，Spring会自动注入resolvedTopicPrefix这个Bean：

  @SpringBootTest
  class ArchiveServiceTest {
  
      @Autowired
      lateinit var archiveService: ArchiveService
  
      @MockBean
      lateinit var fnaReactiveClient: FNAReactiveClient
      
      // 测试方法逻辑保持不变
  }
  

注意：第一种方法启动速度快，适合单元测试；第二种方法更贴近真实环境，但测试启动耗时更长。

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