@Test
public void test_get_parameter_values_as_string_null() throws Exception{

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