如何为调用Service方法的Util类方法编写junit测试用例？

Question

需要为util类（TestInit）方法编写junit测试用例，该方法在内部调用服务方法。

由于util类中的方法调用了服务方法，因此我尝试通过模拟甚至服务调用来编写junit测试。我不确定我是对还是错。

@Repository 
public interface TestRepository  extends JpaRepository<Test, Integer> {
}

public interface TestService {
    public Optional<Test> getTestByCode(String code)
}

@Service
public class TestServiceImpl implements TestService {

@Autowired
private TestRepository testRepo;

@Override
public Optional<Test> getTestByCode(String code) {
    return testRepo.findOneByCode(code);
}
}

@Component
public class TestInit {

@Autowired
TestService testService;

private static String value = null;
public boolean isTestAvail() {
    value = testService.getTestByCode("test");
    return value;
}
}


@RunWith(SpringRunner.class)
public class InitTest {

private TestInit testInit;
private static String value = null;

@TestConfiguration
static class InitTestContextConfiguration {

    @Bean
    public TestService testService() {
        return new TestServiceImpl();
    }
}

@Before
public void init() {
    testInit = new TestInit();
    value = "Random";
}

@MockBean
TestService testService;

@MockBean
private TestRepository testRepository;

@Test
public void testIsSettingsAvaliable() {
    when(testRepository.findOneByCode("value")).thenReturn(value);
    when(testService.getTestByCode("Value")).thenReturn(value);
    assertNotNull(testInit.isTestAvail());
}
}

请有人帮我为util类（TestInit）方法编写junit测试用例，然后再调用service方法。