### Question:
ServiceModel { public long getId() { return (Long) this.reference.getProperty(Constants.SERVICE_ID); } ServiceModel(ServiceReference reference); static List<ServiceModel> services(BundleContext context); String getInterfaces(); long getId(); String getProvidingBundle(); Map<String, String> getProperties();  }### Answer:
@Test public void id() throws Exception { ServiceReference reference = mock(ServiceReference.class); ServiceModel model = new ServiceModel(reference); when(reference.getProperty(Constants.SERVICE_ID)).thenReturn(20l); assertThat(model.getId()).isEqualTo(20l); }