@Test
public void testDescriptorKeys() {

    final Repository mockRepository = mock(Repository.class);
    final String[] keys = new String[]{"SOME_KEY"};
    when(mockRepository.getDescriptorKeys()).thenReturn(keys);
    final RepositoryFacade facade = getFacade(mockRepository);
    assertSame("should be same descriptorKeys",
            keys, facade.getDescriptorKeys());
    final RepositoryFacade facadeNull = getFacade(null);
    assertEquals("should be empty", 0,
            facadeNull.getDescriptorKeys().length);
}