The file outputs nothing. This is deliberate, since it's designed to be run quietly and automatically as a script, not as a web page. So there would be nowhere in normal operation for any output to go.

The way I test it personally, is to tweak the currency rates in the database and then run it in a browser as you have and look in the database to see if they're changed. Then change them again and setup a CRON job for a few seconds into the future and look to see if they've changed. If those work then I set the CRON job to daily shortly after the official update time and check the results the next day.