public class tester{
public static void DublicatRec(List<Contact>con){
        Set<String> StEmail=new Set<String>();
        Set<String> StPhone=new Set<String>();
       
        for(Contact con1 :Con){
            StEmail.add(con1.Email);
            StPhone.add(con1.Phone);
        }
    List<Contact> conList=[select id,name,Email,Phone from Contact where Email IN :StEmail AND Phone IN :StPhone];        

        Map<String,Contact> ConMap=new Map<String,Contact>();
        for(Contact con1 : conList){
            ConMap.put(con1.Email,con1);
            conMap.put(con1.Phone,con1);
        }
        for(Contact con2 :Con)
        {
            if(ConMap.get(con2.Email)!=null){
                con2.addError('Dublicate email');     
            }
            if(ConMap.get(con2.Phone)!=null){
                con2.addError('dublicate phone');
                
            }
        }  
    } 
}



Test Class:

@isTest
public class unitTest {
@isTest
    public Static Void UnitTest(){
        list<Contact> lstCon = new list<Contact>();
        For(Integer i=0;i<5;i++){
            Contact Con = new Contact();
            Con.LastName = 'test ' + i;
            Con.Email = 'test@test.Com';
            Con.Phone = '1234567';
            lstCon.add(Con);
        }

        
        insert(lstCon);
        tester.DublicatRec(lstCon);
    }
}