Hi ,
I have a Apex Trigger which invokes a Apex class  on a Staging table and process the Lead JSON strings and Upserts the leads in Lead table and  links the lead to a Campaign.

This is My Apex class

public class IWS_Utility{

    public static void processLeadStage(List<Lead_Stage__c> lstLeadStage){
   
        Map<Id,Contact> mapExistingContacts = new Map<Id,Contact>();
        Map<String,IWS_Utility.contactDetails> mapContactsToProcess = new Map<String,IWS_Utility.contactDetails>();
        List<Contact_Roles__c> lstContactRoles = new List<Contact_Roles__c>();
        list<IWS_Utility.contactDetails> newContacts = new List<IWS_Utility.contactDetails>() ;  
        map< string, ID >  Campaignname2campaignid = new Map< string, ID >();
        List<CampaignMember> cmcheck = new List<CampaignMember>();
        Set<string> emailIds = new Set<string>() ;
        Set<datetime> messagetimestamp = new Set<datetime>() ;
        Set<string> nonMatchingEmails = new Set<string>() ;

       
        for ( Lead_Stage__c ImportRec : lstLeadStage )
        {
            if(!ImportRec.isProcessed__c){
                ImportRec.isProcessed__c= true;
                IWS_Utility.contactDetails e = IWS_Utility.parseContactFeedItem ( ImportRec.dataContent__c ) ;
                if (e!= NULL) {
                    newContacts.add(e) ;
                    mapContactsToProcess.put(e.emailAddress,e);
                    emailIds.add(e.emailAddress);
                   // messagetimestamp.add(ImportRec.messageTimestamp__c);
                }
            }
        }      
     
      list<CampaignMember> CMs = [
    SELECT id,CampaignId,Campaign.Name from CampaignMember] ;
       
        for ( CampaignMember cmitem : CMs ) {    
          
         
      Campaignname2campaignid.put(cmitem.Campaign.Name,cmitem.Campaignid);   
    
      }
       id Campid =  Campaignname2campaignid.get('Lead Gen Campaign') ;
       system.debug('the camp id is'+ Campid );
       
        List<Contact> lstContacts = [Select Id,AccountId,Email,FirstName,LastName,Phone,(Select Id from Contact_Roles__r where Contact_Role__c = 'Individual Insurance Lead'),(Select Id from CampaignMembers) from Contact where Email In:emailIds limit 1000];
        List<Contact> lstContacts2Update = new List<Contact>();
       
        for(Contact c: lstContacts)
        {
            if(emailIds.contains(c.Email)){
                System.debug('contact exists');
                if(c.FirstName==null || c.Phone==null)
                {
                    if(c.FirstName==null)
                        c.FirstName = mapContactsToProcess.get(c.Email).firstName;
                    if(c.Phone == null)
                        c.Phone = mapContactsToProcess.get(c.Email).phoneNumber;
                    if(c.MailingPostalCode  == null)
                        c.MailingPostalCode = mapContactsToProcess.get(c.Email).zipCode;       
                    lstContacts2Update.add(c); 
                }
                if(c.Contact_Roles__r.size()==0)               
                {
                    lstContactRoles.add(new Contact_Roles__c(Contact__c=c.Id,Account__c=c.Accountid,Contact_Role__c = 'Individual Insurance Lead'));
                }
                if(c.CampaignMembers.size()==0)
                    cmcheck.add(new CampaignMember(ContactId=c.Id,CampaignId =Campid,Status='Responded'));
                    emailIds.remove(c.Email);
            }
        }
       
        List<Lead> lstUpdateLeads = new List<Lead>();       
           
        Database.DMLOptions dmo = new Database.DMLOptions();
        dmo.assignmentRuleHeader.useDefaultRule= true;
       
        for(Lead  l : [Select Id,Email,FirstName,LastName,Phone,(Select Id from CampaignMembers where CampaignId =:Campid ) from Lead where Email In:emailIds]){
            
            if(emailIds.contains(l.Email))
            {
                l.FirstName = mapContactsToProcess.get(l.Email).firstName;
                l.LastName = mapContactsToProcess.get(l.Email).lastName;
                l.Phone = mapContactsToProcess.get(l.Email).phoneNumber;
                l.company =l.FirstName+''+l.LastName ;
                l.postalcode = mapContactsToProcess.get(l.Email).zipCode;
                l.setOptions(dmo);
                lstUpdateLeads.add(l);
                if(l.CampaignMembers.size()==0)
                {
                    cmcheck.add(new CampaignMember(LeadId=l.Id,CampaignId =Campid,Status='Responded'));
                }
                emailIds.remove(l.Email);
            }
        }
       
        List<Lead> lstNewLeads = new List<Lead>();       
      
       
        for(String emailId: emailIds)
        {
            IWS_Utility.contactDetails feedCon = mapContactsToProcess.get(emailId);
            lstNewLeads.add(new Lead(EMail=emailId,Firstname=feedCon.firstName,Phone=feedCon.phoneNumber,postalcode=feedCon.zipCode,LastName=feedCon.LastName,company=feedCon.firstName+' '+feedCon.LastName,LeadSource ='Web'));
        }
       
         for(lead l : lstNewLeads)
           l.setOptions(dmo);
       
        if(lstContacts2Update.size()>0)
            update lstContacts2Update;

        if(lstContactRoles.size()>0)
            insert lstContactRoles;

        if(lstUpdateLeads.size()>0)
            update lstUpdateLeads;
           
        if(lstNewLeads.size()>0){
            insert lstNewLeads;
             system.debug('the camp id is 1'+ Campid );
            for(lead l : lstNewLeads)
                cmcheck.add(new CampaignMember(LeadId=l.Id,CampaignId =Campid,Status='Responded'));
            }
             system.debug(' size is '+ cmcheck.size());
        if(cmcheck.size()>0)
            insert cmcheck;    
    }

    public static contactDetails parseContactFeedItem ( string jsonEnrollmentString ) {
       
        JSONParser parser = JSON.createParser(jsonEnrollmentString);
        contactDetails sr ;

        while (parser.nextToken() != null)
        {
            sr = (contactDetails)parser.readValueAs(contactDetails.class);
        }
        return(sr) ;
    }
   

    public class contactDetails {
       
        public string lastName      {get; set;}
        public string firstName     {get; set;}
        public string emailAddress  {get{return emailAddress.toLowerCase();} set;}
        public string phoneNumber   {get; set;}
        public string zipCode       {get; set;}
    }
   

   

and My Test Class is

@isTest
private class web2lead_test {
    static testMethod void web2lead() {      
    
  Campaign testCampaign;  

   testCampaign = new Campaign(name = 'Lead Gen Campaign');            
  
     Lead a1 = new Lead (
      LastName = 'test1',
      Phone ='1234567890',
      Email = ‘testing@gmail.com’) ;
     insert a1 ;       

   
    Lead L = new Lead (
      FirstName = 'Lead',
      LastName = 'test',
      Company = 'abcde',      
      email = 'testing3@gmail.com' ) ;
     insert L ;
   
     Lead L1 = new Lead (
      FirstName = 'Lead',
      LastName = 'test',
      Company = 'abcd',      
      email = 'testing4@gmail.com' ) ;
     insert L1 ;     
    
  
    CampaignMemberStatus status1 = new CampaignMemberStatus(
        CampaignID = testCampaign.id ,
        Label = 'Responded',
        SortOrder = 2);     
   insert status1 ;  

List<Lead_Stage__c> Leadstagerecord = new List<Lead_Stage__c>() ;
  
    Lead_Stage__c importRecord = new Lead_Stage__c(dataContent__c = '{"firstName":"Teddy","lastName":"Roosevelt","emailAddress":"ro@os.ev","phoneNumber":"","zipCode":"11215"}');
   
    
    Leadstagerecord.add(importRecord) ;
  
   /* Lead_Stage__c importRecord1 = new Lead_Stage__c(dataContent__c = '{"firstName":"Teddy","lastName":"Roosevelt","emailAddress":"ro@os.ev","phoneNumber":"","zipCode":"11215"}');
  
    
    Leadstagerecord.add(importRecord1) ;
 
     Lead_Stage__c importRecord2 = new Lead_Stage__c(dataContent__c = '{"firstName":"Teddy","lastName":"Roosevelt","emailAddress":"testing2@gmail.com","phoneNumber":"1234567890","zipCode":"11215"}');
  
    
     Leadstagerecord.add(importRecord2) ;
 
     Lead_Stage__c importRecord3 = new Lead_Stage__c(dataContent__c = '{"firstName":"Teddy","lastName":"Roosevelt","emailAddress":"testing4@gmail.com","phoneNumber":"","zipCode":"11215"}');
  
    
      Leadstagerecord.add(importRecord3) ;

   Test.startTest();
    insert Leadstagerecord ;
  
    Test.stopTest();

If I run the above test Its throwing an error :

System.DmlException: Insert failed. First exception on row 0; first error: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, IWS_Code.processleadFeedItems: execution of BeforeInsert

caused by: System.DmlException: Insert failed. First exception on row 0; first error: REQUIRED_FIELD_MISSING, Attempted to add a campaign member where either the member id '00Qi000000Gtb1T' or the campaign id 'null' is null.: []

Class.IWS_Code.IWS_Utility.processLeadStage: line 122, column 1


Can Anyone help me out on this?

Thanks