@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());
}