Apex code works, but not during test

I have the following code:

public with sharing class getCustomvalues {
        public final Account account;
        public List<String> myitems {get; set;}
        public List<Custom_items__c> myResult {get;set;}
    
        public getCustomvalues() {
            Id id = ApexPages.currentPage().getParameters().get('id');
            account =  [SELECT Account.Name, items__c FROM Account WHERE Id = :id];
            myitems = new List<String>();
            if (account.items__c== null) {
                 myResult =null;  
                //System.debug(LoggingLevel.ERROR, 'result will be empty');
            } else {
                myitems.addAll(account.items__c.split(';'));
System.debug('myResult Query=select Name,Sn__c,Rn__c from Custom_items__c where Name in '+myitems+' order by Ordering_number__c');
                   myResult =[select Name,Sn__c,Rn__c from Custom_items__c where Name in :myitems order by Ordering_number__c];
            }
        }
        public Account getAccount() {
        
            return account;
        }
}

I wrote a test class that works good, but for some reason the myResult object stays empty.

One thing I noticed was that the debug log showed the following for the query

select Name,Sn__c,Rn__c from Custom_items__c where Name in (thevalue) order by Ordering_number__c

This looks wrong because it should be

select Name,Sn__c,Rn__c from Custom_items__c where Name in ('thevalue') order by Ordering_number__c

So instead of (thevalue) it should be ('thevalue') to be correct.