The Flashlight and Eight Batteries

The problem
8 batteries · 4 work, 4 dead · indistinguishableflashlight needs a working pair

You have 8 batteries. 4 work, 4 are dead — and they're indistinguishable. The flashlight needs two working batteries to turn on. Each attempt is one pair tested.

What is the minimum number of attempts that guarantees the flashlight will turn on?