'test.com'
is optional an optional parameter in that it only provides a reference for subdomain tracking, so you can leave that off and put the code on all your sites; however, if you have subdomain for those 25 sites, you'll run into problems not being able to track (see documentation https://developers.google.com/analytics/devguides/collection/analyticsjs/field-reference#cookieName)
I take it that you are trying to have a Roll-up profile for all of your sites? That's great and all, but I would highly recommend creating a separate property for each, as if your sites' get a lot of traffic, you could run into sampling.
Have you heard of Google Tag Manager - http://www.google.com/tagmanager/ ? I would look into this if you have that many properties, as it will make updating any changes to those tags far easier and take much less of your time.
Ideally, you set it up like this:
1) create a container (apply this container code to all your websites)
2) create 25 Google Analytics Tags in GTM and setup a rule that if {{url}} equals test1.com, then use test1 Google Analytics tag.