final Map<String, Object> map = new LinkedHashMap<>();
        map.put("type", "heartbeat");
        map.put("instanceId", "test-instance");
        map.put("createdTime", 1000L);

        final String json = coordinatorHelper.toJson(map);
        assertNotNull(json);
        assertTrue(json.contains("\"type\":\"heartbeat\""));
        assertTrue(json.contains("\"instanceId\":\"test-instance\""));

#                                                Coordinator
#                                                     ------

# Interval (seconds) for polling heartbeats and events.
coordinator.poll.interval=60
# Time-to-live (ms) for instance heartbeat documents.
coordinator.heartbeat.ttl=180000
# Time-to-live (ms) for operation lock documents.
coordinator.operation.ttl=7200000
# Maximum number of retries for acquiring an operation lock.