TestRestrictContactByName

@isTest
public class TestRestrictContactByName{
    @isTest static void testRestrictContactByName () {	
        Contact c = new Contact(LastName='INVALIDNAME');
        try{
        	insert c;
        }
        catch(DMLException e){
                System.assert(e.getMessage().contains('The Last Name "'+c.LastName+'" is not allowed for DML'));
            }
        }        
    }