Hi Team,
 I need help in building test class for the below Apex Class

@RestResource(urlMapping='/Cortx/CancelOrderService/*')
global class CortxCancelOrderService {
   
    @HttpPost
    global static List<WebResponse> cancelOrders(List<OrderDetail> lstOrderDetail) {
   
        Integration_Log__c LogObj = new Integration_Log__c(Request__c = JSON.serialize(lstOrderDetail));
        insert LogObj;
        Set<String> set_OrderIds = new Set<String>();
        LogObj = [Select Id, Name, Response__c from Integration_Log__c WHERE Id=:LogObj.Id];
        try{
            List<WebResponse> Response = new List<WebResponse>();
            List<Order> lst_Order =  new List<Order>();
            Schema.DescribeSObjectResult r = Order.sObjectType.getDescribe();
            String keyPrefix = r.getKeyPrefix();
           
            for(OrderDetail var :  lstOrderDetail){       
                if(var.Order_Id != null && var.Order_Id.startsWith(keyPrefix) && (var.Order_Id.length() == 15 || var.Order_Id.length() == 18)){
                    set_OrderIds.add(var.Order_Id);
                }
            }  
            Map<Id, Order> map_Orders = new Map<Id, Order>([Select Id, Status, Cancel_Reason__c from Order Where Id IN:set_OrderIds]);
            List<Services_and_Equipment__c> lst_SE = [ Select Id, Order__c, Cortx_Service_Id__c from Services_and_Equipment__c WHERE Order__c  != null AND Order__c IN:map_Orders.keySet()];
            Map<Id, List<Services_and_Equipment__c>> map_Order2lstSE = new Map<Id, List<Services_and_Equipment__c>> ();
            for(Services_and_Equipment__c var : lst_SE ){
                if(map_Order2lstSE.containsKey(var.Order__c)){
                    map_Order2lstSE.get(var.order__c).add(var);
                }else{
                    List<Services_and_Equipment__c> lst_tmp = new List<Services_and_Equipment__c>{var};
                    map_Order2lstSE.put(var.order__c, lst_tmp);
                }
            }
            List<Services_and_Equipment__c> lst_SE_ToUpdate = new List<Services_and_Equipment__c>();
            Set<String> OrderIdsToUpdate = new Set<String>();
            for(OrderDetail var :  lstOrderDetail){       
                if(var.Order_Id != null && var.Order_Id.startsWith(keyPrefix)){
                    if(var.Order_Id.length() == 18 && map_Orders.containsKey(var.Order_Id)){
                        // Here We need to put data validation before update the Order status as Cancelled
                       
                       
                        if(var.CancelReason != null){
                            Order Order_Obj = new Order(Id=var.Order_Id, Cancel_Reason__c = var.CancelReason, status='Cancelled');
                            for(Services_and_Equipment__c se_var : map_Order2lstSE.get(var.Order_Id)){
                                se_var.Order__c = null;
                                se_var.Cortx_Service_Id__c = null;
                                lst_SE_ToUpdate.add(se_var);
                            }
                            OrderIdsToUpdate.add(var.Order_Id);
                            lst_Order.add(Order_Obj);
                        }else{
                            WebResponse Response_Obj = new WebResponse();
                            Response_Obj.Order_Id = var.Order_Id;
                            String ErrorMsg = 'CancelReaon is mandatory to cancel Order "'+ var.Order_Id ;
                            Response_Obj.Status = 'Failure';
                            Response_Obj.StatusDescription = ErrorMsg;
                            Response.add(Response_Obj);
                        }                    
                    }else{
                        WebResponse Response_Obj = new WebResponse();
                        Response_Obj.Order_Id = var.Order_Id;
                        String ErrorMsg = 'Order Record with Id "'+ var.Order_Id +'" not found in System';
                        Response_Obj.Status = 'Failure';
                        Response_Obj.StatusDescription = ErrorMsg;
                        Response.add(Response_Obj);
                    }
                }else{
                    WebResponse Response_Obj = new WebResponse();
                    Response_Obj.Order_Id = var.Order_Id;
                    String ErrorMsg = 'Order_Id field can not be null';
                    Response_Obj.Status = 'Failure';
                    Response_Obj.StatusDescription = ErrorMsg;
                    Response.add(Response_Obj);
                }
            }
            Database.SaveResult[] SR_OrderUpdate = Database.update(lst_Order, false);    
            Database.SaveResult[] SR_SE_Update = Database.update(lst_SE_ToUpdate, false);    
           
            for (Database.SaveResult sr : SR_OrderUpdate ) {
                WebResponse Response_Obj = new WebResponse();
                if (sr.isSuccess()) {
                    Response_Obj.Order_Id = sr.getId();
                    Response_Obj.Status = 'Success';
                    Response_Obj.StatusDescription = 'Order cancelled successfully. SFDC log number - '+ LogObj.Name;
                }
                else {                       
                    Response_Obj.Order_Id = sr.getId();
                    String ErrorMsg = 'The following error has occurred.';              
                    for(Database.Error err : sr.getErrors()) {
                        ErrorMsg = ErrorMsg +' '+ err.getStatusCode() + ': ' + err.getMessage();
                    }
                    Response_Obj.Status = 'Failure';
                    Response_Obj.StatusDescription = ErrorMsg + ' SFDC log number - '+ LogObj.Name;
                }
                Response.add(Response_Obj);
            }      
            LogObj.Response__c = JSON.serialize(Response);
            LogObj.Is_Success__c = true;
            update LogObj;
            System.debug('--------WebResponse---- '+ Response);
            return Response;
        }catch(Exception ex){
            WebResponse ExceptionResponse_Obj = new WebResponse();
            ExceptionResponse_Obj.Status = 'Failure';
            ExceptionResponse_Obj.StatusDescription = ex.getMessage();
            LogObj.Response__c = JSON.serialize(ExceptionResponse_Obj);
            LogObj.Is_Success__c = false;
            update LogObj;
            System.debug('--------WebResponse---- '+ ExceptionResponse_Obj);
            return new List<WebResponse>{ExceptionResponse_Obj};
        }
    }

    global class OrderDetail{
        global String Order_Id;          // SFDC Order Id 18 digit
        global String CancelReason;
        global OrderDetail(){}
    }
    global class WebResponse{
        global String Order_Id{get;set;}     // SFDC Order Id 18 digit
        global String Status{get;set;}             // Success or Failure
        global String StatusDescription{get;set;}  // Detail of Failure, In case of success it will have default value “Record Updated Successfully”
    }

}