2006 Chevy Trailblazer Fuel pump

Electrical problem
2006 Chevy Trailblazer 6 cyl Two Wheel Drive 59000 miles

I purchased a new fuel pump. Before installing the new pump, it was tested with an auto light tester. The light on the tester wouldn't even glow. The new fuel pump wasn't getting any power. The fuel pump relay is also new, and it is working properly. When you turn on the ignition, the fuel pump relay makes a clicking noise, and it also clicks when you turn off the switch. No sound is heard from the fuel pump. Other than the fuel pump relay, what other electrical unit controls the fuel pump? How is it possible for the fuel pump relay to be working and fuel pump isn't?