Testing DRL's is not that difficult, at least on the 2009 LT's.
Check the lighting schematic on your year before you try this but, on the '09, both the DRL bulbs are grounded on one side then, the hot or +12v side goes through a 15 amp fuse (31, under hood box) and to the normally open contact of the DRL relay. That means, the fuse and the DRL bulbs are totally isolated from their control circuit when the truck is off. Sooo you can safely put +12 volts on the DRL fuse and it will light up the bulbs. Naturally, you have already checked the fuse and, if blown, change it and test using the trucks normal control circuit. If the fuse blows again, you have a short and DO NOT use the method I have suggested.
If the bulbs don't light, check them first, if they are good then the wiring or the sockets to the bulbs. If they do light using this test method then the problem is the DRL relay or the BCM or something that feeds the BCM.
I had two bad bulbs... replaced them with LED's. Significant heat syncs on the ones in the picture below... hope they last awhile. Make sure when you plug them in that you test them first before you re-install your headlights to make sure they light up nice and bright. These maybe polarity (which way you plug them in) sensitive on some trucks.
A note on the 2009 LT's... You do not have to remove the forward wheel well covers to access any bracket-bolt arrangement like some other years. Just remove the two top bolts (obvious where they are) and gently pull the headlight forward. The headlights are secured with standard push-in friction pins even at the bottom outer edge.