assertFalse(queryFieldConfig.isSortField("invalid"));
        assertFalse(queryFieldConfig.isSortField(""));
        assertFalse(queryFieldConfig.isSortField(null));
    }

    @Test
    public void test_isFacetField() {
        String[] facetFields = { "category", "type", "author", "date" };
        queryFieldConfig.setFacetFields(facetFields);

        // Test valid facet fields