So I searched for a little bit but I couldn't find anything conclusive.

Basically, I just built a 2x12 cab with mah dad and I wanna test it out, but, I don't own a head. So how do I do it? I have a Fender Frontman 15G and a Randall RX50D, neither of which have cabinet outs. Can I test it with them somehow? I read somewhere you can run a cabinet through the headphone jack of an amp but I wasn't sure. So, help guys? Also if this is in the wrong forum, just tell me where to put it and I'll be on my way.
Thanks in advance