assertTrue(mockConfig.getApiPingEsFieldSet().contains("cluster_name"));
        assertTrue(mockConfig.getApiPingEsFieldSet().contains("status"));
    }

    @Test
    public void test_emptyFieldSet() {
        // Test with empty field set
        FessConfig mockConfig = new FessConfig.SimpleImpl() {
            private static final long serialVersionUID = 1L;

            @Override