模拟单例实例并验证（模拟）失败

Question

我有一个实现类，它实现一个接口并覆盖其方法。实现类获取类的单例实例，需要在JUnit中对其进行模拟。我尝试使用PowerMock，但在这里无法正常使用。 另外，在运行此处提到的测试时，我得到此处提到的错误：https://codeshare.io/5NyJyr

这是实现类：

@Slf4j
@Component
public class PhoneServiceImpl implements NotificationService {

    private String notificationServiceURL;
    private PhoneContext phoneContext;

    public PhoneServiceImpl(@Value("${notificationService.url}") String notificationServiceURL) {
        this.notificationServiceURL = notificationServiceURL;
    }

    @Override
    public void sendPhoneSMSByEmployeeIds(String title, String message, List<String> employeeIds) {
        log.info("Sending notifications by Employee Id");

        SendNotificationByEmployeeIds sendNotificationByEmployeeIds = SendNotificationByEmployeeIds.getInstance();
        sendNotificationByEmployeeIds.setNotificationServiceURL(notificationServiceURL);
        phoneContext = new PhoneContext(sendNotificationByEmployeeIds);
        phoneContext.notify(title, message, employeeIds);
    }
}

测试：

public class Test {

    PhoneServiceImpl phoneServiceImpl;

    @Mock
    PhoneContext phoneContext;

    @Value("${phoneService.url}")
    String phoneServiceUrl;

    @BeforeEach
    void setUp() {
        MockitoAnnotations.openMocks(this);
        phoneServiceImpl = new PhoneServiceImpl("some");
    }

    @org.junit.jupiter.api.Test
    void simpleTest() {
        phoneServiceImpl.sendPhoneSMSByEmployeeIds(anyString(), anyString(), anyList());
        verify(phoneContext, Mockito.times(1)).notify(anyString(), anyString(), anyList());
    }
}