### Question:
SiteMapConfigurationImpl implements SiteMapConfiguration { @Override public UrlExternalizer getUrlExternalizer() { return getNamedService(UrlExternalizer.class, config.urlExternalizer()); }  @Activate void activate(final SiteMapConfigurationImplConfig config); @Deactivate void deactivate(); @Override Pattern getPagePathPattern(); @Override PageRecognizer getPageRecognizer(); @Override UrlExternalizer getUrlExternalizer(); @Override Map<String, String> getXmlNamespaces(); @Override Collection<PropertyProvider> getPropertyProviders(); @Override Set<String> getMandatoryCachedPaths();  }### Answer:
@Test public void getUrlExternalizer() { when(config.urlExternalizer()).thenReturn(X); assertNull(model.getUrlExternalizer()); final UrlExternalizer externalizer = mock(UrlExternalizer.class); when(serviceRetriever.getNamedService(UrlExternalizer.class, X)).thenReturn(externalizer); assertEquals(externalizer, model.getUrlExternalizer()); }