Hi Everyone,

I was new to write a apex test class.please find the below code and help me how to write a test class for that and if possible please explain me line by line it well really helpful for me.Thanks inadvance.

@RestResource(urlMapping='/DeleteInfo/*')
global class DeleteInfo {
@HttpPost
    global static String doPost() {
        String responseJSON;
        if (RestContext.request.requestBody != null) {
            String requestStatus;
            String reqBody = RestContext.request.requestBody.toString();
            String parentId = null;
            Request Request = new Request();
            String environmentCode = Utility.getEnvironmentCode(UserInfo.getUserName());
            
            try {
                Req req = (Req)JSON.deserialize(reqBody, DeleteInfo.Req.class);
                Request = req.Request;
                
                if (Request.parent != null) {
                    if (Request.parent.StarID != null && Request.parent.StarID != '') {
                        String parentStarID = Request.parent.StarID + '__' + environmentCode;
                        List<Hub_Parent__c> ptList = [select Id from Hub_Parent__c where StarIDt__c = :parentStarID Limit 1];
                        
                        if (ptList.size() > 0) {
                            Hub_Parent__c objparent = ptList[0];
                            parentId = objparent.Id;
                            
                            DataDelete.DataDelete(objParent.Id);
                            
                            responseJSON = InboundTransactionResponse.GetSucessResponse(Request.Header.TransactionType, Request.Header.TimeStamp, Request.Header.FileID, Request.parent.StarID);
                            requestStatus = 'Success';
                        }
                        else {
                            responseJSON = InboundTransactionResponse.GetErrorResponse(Request.Header.TransactionType, Request.Header.TimeStamp, Request.Header.FileID, Request.parent.StarID, 'StarID', '0056', 'StarID doesn\'t exists in system');
                            requestStatus = 'Failure';
                        }
                    }
                    else {
                        responseJSON = InboundTransactionResponse.GetErrorResponse(Request.Header.TransactionType, Request.Header.TimeStamp, Request.Header.FileID, null, 'StarID', '001', 'StarID is a required field.');
                        requestStatus = 'Failure';
                    }
                }
                else {
                    responseJSON = InboundTransactionResponse.GetErrorResponse(Request.Header.TransactionType, Request.Header.TimeStamp, Request.Header.FileID, null, 'parent', '001', 'Invalid request format.');
                    requestStatus = 'Failure';
                }
                BlueStarTransactionDetails.CreateInboundTransactionRequest(Request.Header.TransactionType, Request.Header.FileID, requestStatus, reqBody, responseJSON, null, null, null, environmentCode);
            }
            catch (Exception ex) {
                System.debug('Delete Exception: ' + ex.getMessage());
                String fileId;
                if (Request.Header != null && Request.Header.FileID != null) {
                    fileId = Request.Header.FileID;
                }
                else {
                    fileId = 'Unknown';
                }
                BlueStarTransactionDetails.CreateInboundTransactionRequest(Request.Header.TransactionType, fileId, 'Exception', reqBody, ex.getMessage(), null, null, null, environmentCode);
                if(Request != null && Request.Header != null){
                  responseJSON = InboundTransactionResponse.GetErrorResponse(Request.Header.TransactionType, Request.Header.TimeStamp, Request.Header.FileID, null, 'Error', '0056', ex.getMessage());
                }else{
                    responseJSON = ex.getMessage();
                }
            }
        }
        return responseJSON;
    }
    
    public class parent {
        public String StarID {get;set;}
    }
    
    public class Header {
        public String TransactionType {get;set;}
        public String TimeStamp {get;set;}
        public String FileID {get;set;}
    }
    
    public class Request {
        public parent parent {get;set;}
        public Header Header {get;set;}
    }
    
    public class Req {
        public Request Request {get;set;}
    }
}

Thanks inadvance.