trigger RequireRejectionPartReg on Lead (before update) {

    Map<Id, Lead> rejectLeads = new Map<Id, Lead>{};
        Id gd = Schema.SObjectType.Lead.RecordTypeInfosByName.get('GlobalPRM Partner Registration').RecordTypeId;
        for(Lead ld : Trigger.new){

    
            if((ld.Rejection_Reason__c ==null && ld.Registration_Status__c =='Rejected')){
                if(ld.RecordTypeId == gd){
                rejectLeads.put(ld.id, ld);
                    rejectLeads.get(ld.id).addError('Operation Cancelled: Please provide a rejection reason on the Lead!');
                }
                
            }
            if(!rejectLeads.isEmpty()){
                List<Id> processInstanceIds = new List<Id>{};
                    for(Lead lds: [SELECT(SELECT Id FROM ProcessInstances ORDER BY CreatedDate DESC LIMIT 1) FROM Lead WHERE Id IN :rejectLeads.keySet()]){
                        if(processInstanceIds.size() > 0){
                        processInstanceIds.add(lds.ProcessInstances[0].Id);  
                        }
            
                                           
                    }
                for(ProcessInstance pi : [SELECT TargetObjectId,(SELECT Id, StepStatus, Comments FROM Steps ORDER BY CreatedDate DESC LIMIT 1) FROM ProcessInstance WHERE Id IN : processInstanceIds ORDER BY CreatedDate DESC]){
                    if((pi.Steps[0].StepStatus == 'Rejected')){
                        rejectLeads.get(pi.TargetObjectId).addError('Operation Cancelled: Please provide a rejection reason on the Lead!');
                    }
                }
            }
            
        }
    
}

@isTest
public class TestRequireRejection {

     static testMethod void testRequireRejectMethod(){
         test.startTest();
         Id gl = [SELECT Id FROM RecordType WHERE Name='GlobalPRM Partner Registration' AND SObjectType='Lead' limit 1].Id;
        Lead l = new lead();
         l.FirstName = 'test';
         l.LastName = 'mctesty';
         l.LeadSource = 'Banner';
         l.Company = 'Test Company';
         l.Business_Segment__c = 'Connect';
         l.RecordTypeId = gl;
         l.Region__c = 'EMEA';
         l.Areas_of_Interest__c = 'Readers';
         l.Role__c = 'End-User';
         l.Rejection_Reason__c = '';
         
         insert l;
         
         Lead upl = [SELECT Id, Registration_Status__c FROM Lead WHERE Id = :l.id];
         
         upl.Registration_Status__c = 'Rejected';
         
         try{
             
         	update upl;
             system.debug(upl);
         }
         catch(Exception e){
             
             system.debug(e.getMessage());
             Boolean expectedException = e.getMessage().contains('Operation Cancelled: Please provide a rejection reason on the Lead!') ? true: false;
             system.assertEquals(expectedException, true);
             
         }
                        
             Approval.ProcessSubmitRequest app = new Approval.ProcessSubmitRequest();
             app.setObjectId(upl.id);
         	 app.setNextApproverIds(new Id[] {UserInfo.getUserId()});
             Approval.ProcessResult result = Approval.process(app);
 
                 
            test.stopTest();
         
    }  
}