@Test
public void getPropertyProviders() {

    Collection<PropertyProvider> propertyProviders = model.getPropertyProviders();
    assertNotNull(propertyProviders);
    assertTrue(propertyProviders.isEmpty());
    when(config.propertyProviders()).thenReturn(new String[] { X, Y });
    when(serviceRetriever.getNamedService(PropertyProvider.class, X)).thenReturn(mock(PropertyProvider.class));
    when(serviceRetriever.getNamedService(PropertyProvider.class, Y)).thenReturn(mock(PropertyProvider.class));
    propertyProviders = model.getPropertyProviders();
    assertNotNull(propertyProviders);
    assertFalse(propertyProviders.isEmpty());
    assertEquals(2, propertyProviders.size());
}