After execution of test ,Its showing errors for these two fields--

  FAM3.Fi_Agent__c='FAMagent3';
  FAM3.PinCode__c='400 003';

Main Class::::

public class AgentMappingTriggerHandlerException  extends Exception {
public static void afterInsert(map<Id, FI_Agent_Mapping__c> oldMap, map<Id, FI_Agent_Mapping__c> newMap, List<FI_Agent_Mapping__c> newList){
    
        Map<String,String> AgentMappingMap = new Map<String,String>();
        Map<String,String> GroupMap = new Map<String,String>();
        Map<String,String> agentmappingUserMap = new Map<String,String>();
        List<String> AgencyList  = new List<String>();
        
        for(Sobject obj : newList){
            AgentMappingMap.put(String.valueOf(obj.get('Id')),String.valueOf(obj.get('Agency_Name__c')));
            AgencyList.add(String.valueOf(obj.get('Agency_Name__c')));
        }
    system.debug('AgentMappingMap==='+AgentMappingMap);
    
        
        String groupquery='select id,name from Group where name in: AgencyList';
        List<Sobject> targetobj=Database.query(groupquery);
        if(targetobj.size() > 0){
            for(Sobject obj : targetobj){
                GroupMap.put(String.valueOf(obj.get('Name')),String.valueOf(obj.get('Id')));   
                
            }
            system.debug('Group Map==='+GroupMap);
        }
    
     for(Sobject obj : newList){
            agentmappingUserMap.put(String.valueOf(obj.get('Id')),GroupMap.get(String.valueOf(AgentMappingMap.get(String.valueOf(obj.get('Id'))))));
     system.debug('agentmappingUserMap=='+agentmappingUserMap);   
     }
    
        SharingUtility.agentMappingShareRecord(agentmappingUserMap,'Edit', 'Manual');        
     }
    
    public static void beforeUpdate(map<Id, FI_Agent_Mapping__c> oldMap, map<Id, FI_Agent_Mapping__c> newMap, List<FI_Agent_Mapping__c> newList){
           
    }

    public static void afterUpdate(map<Id, FI_Agent_Mapping__c> olaMap, map<Id, FI_Agent_Mapping__c> newMap, List<FI_Agent_Mapping__c> newList){
    }
   
    public static void beforeInsert(List<FI_Agent_Mapping__c> AgentMappingList){
       
        List<String> useridList = new List<String>();
        List<Id> pincodeList = new List<Id>();
        for(FI_Agent_Mapping__c obj : AgentMappingList){
            useridList.add(String.valueOf(obj.get('Fi_Agent__c')));
            pincodeList.add(obj.PinCode__c);
        }
        String agentmappingquery='select id,Pincode_Map__c,Fi_Agent__c from FI_Agent_Mapping__c where PinCode__c in: pincodeList';
        List<FI_Agent_Mapping__c> targetobj=Database.query(agentmappingquery);
        if(targetobj.size() > 0){
            AgentMappingList.get(0).addError( 'User Has already Mapped to the same pincode');   
        }
    } 
}

Please Correct my Test class:::

@isTest
public class AgentMappingTriggerHandlerExceptionTest {
    
@isTest         
    public static void afterInsertTest(){
    
     FI_Agent_Mapping__c FAM1 = new FI_Agent_Mapping__c();
      FAM1.Name ='FAMname1';
      FAM1.Agency_Name__c='A R ASSOCIATES';
      FAM1.Fi_Agent__c='FAMagent1';
      FAM1.PinCode__c='400 001';
      insert FAM1;
      
      FI_Agent_Mapping__c FAM2 = new FI_Agent_Mapping__c();
      FAM2.Name ='FAMname2';
      FAM2.Agency_Name__c= 'COGENT';
      FAM2.Fi_Agent__c='FAMagent2';
      FAM2.PinCode__c='400 002';
      insert FAM2;
       
      
      Map<Id,FI_Agent_Mapping__c> afterInsertMap  =  New Map<Id,FI_Agent_Mapping__c>();
      FI_Agent_Mapping__c FAM3 = new FI_Agent_Mapping__c();
      FAM3.Name ='FAMname3';
      FAM3.Agency_Name__c= 'BEST SERVICES';
      FAM3.Fi_Agent__c='FAMagent3';
      FAM3.PinCode__c='400 003';
      insert FAM3;
      afterInsertMap.put(FAM3.Id,FAM3);
      
      List<FI_Agent_Mapping__c> newListA = new List<FI_Agent_Mapping__c>();
      FI_Agent_Mapping__c FAM4 = new FI_Agent_Mapping__c();
      FAM4.Name ='FAMname4';
      FAM4.Agency_Name__c='BANRAD FINSERV';
      FAM4.Fi_Agent__c='FAMagent4';
      FAM4.PinCode__c='400 004';
      insert FAM4;
      newListA.add(FAM4);
        
       Test.startTest();
       AgentMappingTriggerHandlerException.afterInsert(afterInsertMap,afterInsertMap,newListA ); 
       Test.stopTest();
      
    }
@isTest
    public static void beforeUpdateTest(){
        
    }
@isTest
    public static void afterUpdateTest(){
        
    }
@isTest
    public static void beforeInsertTest(){
    
    }
}