@Test
public void test_get_sub_parameter_values_as_string_null() throws Exception{

    when(dataObjectService.find(Matchers.argThat(new ClassOrSubclassMatcher<ParameterBo>(
            ParameterBo.class)), any(QueryByCriteria.class))).thenReturn(null);
    Collection<String> values = getParameterRepositoryService().getSubParameterValuesAsString(key, "foo");
    assertTrue(values.isEmpty());
    assertImmutableList(values);
    verify(dataObjectService, times(2)).find(Matchers.argThat(new ClassOrSubclassMatcher<ParameterBo>(
            ParameterBo.class)), any(QueryByCriteria.class));
}