This is what I use to test the emergency lights at our facility:
a pole that is designed for painting (constructed of fiberglass and aluminum) which extends several feet (reaches a total of 12'); the end has an attachment that was designed by our maintenance department especially for this purpose so that it can press the testing button whether it be on the side or the bottom of the emergency lights (basically an aluminum box that has a pointer on the top and the side) - also, one of our maintenance personnel has a wooden pole that has been formed at the end to press the button - both work great.
You should be able to purchase the paint pole like I have at your local hardware store (about $20), and then you will need someone to design and construct an end for you. Or you can purchase a wooden pole, which may be much easier to modify yourself.
We test our lights every month to ensure they are still working properly. Hope this helps you. If you have any questions or if you would like a photo of the pole I use let me know and I'll email it to you.
Tim Croley,
Safety Coordinator
CMCA