private LinkCallDataMap createLinkCallDataMap(String fromAgentId, ServiceType fromAgentServiceType, String toAgentId, ServiceType toAgentServiceType, HistogramSlot slot, long callCount) {
        long currentTimestamp = System.currentTimeMillis();
        LinkCallDataMap linkCallDataMap = new LinkCallDataMap();
        linkCallDataMap.addCallData(new Application(fromAgentId, fromAgentServiceType), new Application(toAgentId, toAgentServiceType), currentTimestamp, slot.getSlotTime(), callCount);
        return linkCallDataMap;
    }
Checks histograms for user node.
<pre>
    userNode ---> wasNode (2 agents)
</pre>
web/src/test/java/com/navercorp/pinpoint/web/applicationmap/appender/histogram/NodeHistogramAppenderTest.java