@Override
    public void leftCluster() {
        final String nodeName = xmppServer.getServerInfo().getHostname();
        LOGGER.info("This node ({}/{}) has left the cluster", xmppServer.getNodeID(), nodeName);
        sendMessageToAdminsIfEnabled("The local node ('" + nodeName + "') has left the cluster - this node no longer has any resilience");
    }
@Test
    public void whenThisNodeLeavesTheClusterAMessageWillBeSent() {

        clusterMonitor.leftCluster();

        verify(xmppServer).sendMessageToAdmins(any());
    }