i found a nice code for checking user workflow hierarchy approver and solved the related error.

static void navax_workflowHierarchyTester(Args _args)
{
    WorkflowTypeName                    workflowTemplateName = 'TIDEmploymentLeave';
    //TrvExpTrans                         trvExpTrans;
    //TrvExpNumber                        trvExpNum = '000015'; //Expense id

    HcmEmploymentLeave                  hcmEmploymentLeave;
    str                                 nodeId = '23511014'; //Starting worker id
    WorkflowHierarchyLevel              level = 0;
    WorkflowContext                     workflowContext;
    SysWorkflowTable                    workflowTable;
    WorkflowLimitHierarchyProvider      workflowLimitHierarchyProvider;
    WorkflowHierarchyProviderNode       workflowHierarchyProviderNode;
    HRPWorkerLimit                      workerLimit = new HRPWorkerLimit();
    HcmWorker                           hcmWorker;
    DirPersonUser                       dirPersonUser;
    RefRecId                            hcmPositionRecId;
    HcmPosition                         hcmPosition;
    container                           spendingCon, approvalCon;
    UserId                              userId;

    select firstOnly workflowTable
        where workflowTable.TemplateName == workflowTemplateName;

    select firstOnly hcmEmploymentLeave
        where hcmEmploymentLeave.HRSLeaveReqId ==  "LV-00635" ;

    workflowContext = WorkflowContext::newWorkflowContext(
        curext(),
        tableNum(hcmEmploymentLeave),
        hcmEmploymentLeave.RecId,
        workflowTable.WorkflowCorrelationId);

    workflowLimitHierarchyProvider = new WorkflowLimitHierarchyProvider();

    //Level 1
    while (nodeId && level < 20) //20 is just a fall back. In case it goes into an endless loop.
    {
        workflowHierarchyProviderNode   = workflowLimitHierarchyProvider.getNextNode(nodeId, level, workflowContext);
        nodeId                          = workflowHierarchyProviderNode.getnodeId();
        hcmWorker                       = HcmWorker::findByPersonnelNumber(nodeId);
        userId                          = DirPersonUser::findParty(hcmWorker.Person).User;
        hcmPositionRecId                = HcmWorker::getPrimaryPosition(hcmWorker.RecId);
        hcmPosition                     = HcmPosition::find(hcmPositionRecId);

        spendingCon = workerLimit.getWorkerSigningLimit(
            hcmWorker.RecId,
            SourceDocumentRelationType::ExpenseReport,
            HRPLimitType::Spending,
            hcmPosition.PositionId);

        approvalCon = workerLimit.getWorkerSigningLimit(
            hcmWorker.RecId,
            SourceDocumentRelationType::ExpenseReport,
            HRPLimitType::Approval,
            hcmPosition.PositionId);

        info(strFmt("UserId: %1 | WorkerId: %2 | PositionId: %3 | ReportsToPosition: %4 | SpendingLimit: %5 | ApprovalLimit: %6",
            userId,
            hcmWorker.PersonnelNumber,
            hcmPosition.PositionId,
            hcmPosition.reportsToPosition(),
            con2Str(spendingCon),
            con2Str(approvalCon)
            ));

        level++;
    }
}

source :
https://community.dynamics.com/ax/b/dynamicsnavax/archive/2015/06/08/workflow-hierarchy-assignment-common-errors-explained-and-tester-job-ax-2012