final String json = "{\"type\":\"heartbeat\",\"instanceId\":\"test\",\"createdTime\":12345}";
        final Map<String, Object> result = coordinatorHelper.parseJson(json);
        assertEquals("heartbeat", result.get("type"));
        assertEquals("test", result.get("instanceId"));
        assertEquals(12345, result.get("createdTime"));
    }

    @Test
    public void test_parseJson_empty() {

        doc.put("url", "https://example.com");
        doc.put("title", "Test Title");
        doc.put("role", "Rguest");
        doc.put("boost", "1.0");
        doc.put("content_length", "12345");
        doc.put("click_count", "100");

        final List<String> errors = new ArrayList<>();
        AdminSearchlistAction.validateFields(doc, messages -> {
            errors.add("error");
        });