Mockito单元测试中when(..)服务方法存根不生效问题排查

核心原因：Spring上下文覆盖了Mock对象 #

你使用了@SpringBootTest注解，该注解会启动完整的Spring应用上下文。此时Ar11Application作为标注@SpringBootApplication的类，会被Spring自动实例化，其内部@Autowired的ar11ApplicationService会被注入真实的Ar11ApplicationServiceImpl实例。你通过@InjectMocks创建的测试用Ar11Application实例，会被Spring容器中的实例覆盖，导致run方法调用的是真实服务而非mock对象。

额外问题：JUnit注解冲突 #

测试类混合使用了@RunWith(MockitoJUnitRunner.class)（JUnit4运行器）和@ExtendWith(MockitoExtension.class)（JUnit5扩展），属于冗余配置且可能引发冲突。由于你使用了JUnit5的@BeforeEach和org.junit.jupiter.api.Assertions，应当移除@RunWith注解。

方案一：使用@SpringBootTest + @MockBean（推荐，保留Spring上下文） #

这种方式让Spring将mock服务替换容器中的真实实现，同时保留Spring自动配置（如@Value属性注入）：

@SpringBootTest
@ExtendWith(MockitoExtension.class)
class Ar11ApplicationTest {

    // 用@MockBean替代@Mock，Spring会将该mock实例注入容器
    @MockBean
    Ar11ApplicationService ar11ApplicationService;
    
    @MockBean
    EmailService emailService;

    // 直接@Autowired获取Spring管理的Ar11Application实例，自动注入mock服务
    @Autowired
    Ar11Application ar11Application;
    
    @BeforeEach
    void setUp() throws Exception {
        Mockito.when(ar11ApplicationService.processEligibleRecords(
                Mockito.anyString(), Mockito.anyString(), 
                Mockito.anyString(), Mockito.anyString(), 
                Mockito.anyString(), Mockito.anyString(), 
                Mockito.anyString(), Mockito.anyInt(), Mockito.anyString()))
              .thenReturn(new Ar11ResultBean());
    }

    @Test
    void main() throws Exception {
        org.junit.jupiter.api.Assertions.assertDoesNotThrow(
            () -> ar11Application.run(new String[] {})
        );
    }
}

方案二：纯Mockito测试（不加载Spring上下文） #

若无需Spring自动配置，仅测试Ar11Application的逻辑，可移除@SpringBootTest，手动设置@Value属性值：

@ExtendWith(MockitoExtension.class)
class Ar11ApplicationTest {

    @Mock
    Ar11ApplicationService ar11ApplicationService;
    
    @Mock
    EmailService emailService;
    
    @InjectMocks
    Ar11Application ar11Application;
    
    @BeforeEach
    void setUp() throws Exception {
        // 手动设置@Value注入的属性值（纯Mockito不处理@Value）
        ReflectionTestUtils.setField(ar11Application, "eligibleFilename", "test-eligible.txt");
        ReflectionTestUtils.setField(ar11Application, "newFilenamePrefix", "test-new-");
        ReflectionTestUtils.setField(ar11Application, "sftpUserName", "test-user");
        ReflectionTestUtils.setField(ar11Application, "sftpPrivateKeyPath", "/test/path");
        ReflectionTestUtils.setField(ar11Application, "sftpPrivateKeyPassphrase", "test-pass");
        ReflectionTestUtils.setField(ar11Application, "sftpHost", "test-host");
        ReflectionTestUtils.setField(ar11Application, "sftpPort", 22);
        ReflectionTestUtils.setField(ar11Application, "sourceDir", "/test/source");
        ReflectionTestUtils.setField(ar11Application, "remoteDir", "/test/remote");

        // 存根设置不变
        Mockito.when(ar11ApplicationService.processEligibleRecords(
                Mockito.anyString(), Mockito.anyString(), 
                Mockito.anyString(), Mockito.anyString(), 
                Mockito.anyString(), Mockito.anyString(), 
                Mockito.anyString(), Mockito.anyInt(), Mockito.anyString()))
              .thenReturn(new Ar11ResultBean());
    }

    @Test
    void main() throws Exception {
        org.junit.jupiter.api.Assertions.assertDoesNotThrow(
            () -> ar11Application.run(new String[] {})
        );
    }
}

内容的提问来源于stack exchange，提问作者gene b.