I have created a batchable class for a production system. If following code doesn't work, any code does not work.

The code is in production system now. It takes daily exchange rates from a site everyday and creates Currency__c records. If it works when exchange rates haven't published, it takes last day exchange rates. But it does not work the way I want and I would like to test it at debug logs.

Following method "getXML(Date today)" has never invoked when I viewed debug logs. Therefore System.debug('test: ' + result); has also never invoked.

How can I see this log?

public String getXML(Date today){  
    counter += 1;       
    if(counter == 11) return '';
    try{
        Http h = new Http();
        HttpRequest req = new HttpRequest();       

        String m = today.month() + '';
        if((today.month()+'').length()==1) m = '0' + today.month();
        String d = today.day() + '';
        if((today.day()+'').length()==1) d = '0' + today.day();
        String donem = today.year() + '' + m;
        String formattedDate = d + '' + m + today.year();

        req.setEndpoint('http://www.tcmb.gov.tr/kurlar/' + donem + '/' + formattedDate + '.xml'); 
        req.setMethod('GET');            
        String result = '';
        if (!Test.isRunningTest()){
            HttpResponse res = h.send(req);
            result = res.getBody();
        }
        else {
            result += 'test';
        }         
        System.debug('test: ' + result);
        if(res.getStatusCode()==404){
            return getXML(today.addDays(-1));
        }   
        return result;
    }catch(Exception e){
        return getXML(today);
    }
}