public NodeMgr getNodeMgr() {
        return nodeMgr;
    }
@Test(expected = DdlException.class)
    public void testUpdateModifyCurrentMasterException() throws Exception {
        GlobalStateMgr globalStateMgr = mockGlobalStateMgr();
        ModifyFrontendAddressClause clause = new ModifyFrontendAddressClause("test-address", "sandbox-fqdn");
        // this case will occur [can not modify current master node] exception
        globalStateMgr.getNodeMgr().modifyFrontendHost(clause);
    }