Pedal induce BOB test.
With both brakes locked up and the rider sitting on the bike with support so he does not fall over. Accelerate without any up down motion from the rider not allowing the bike to move forward because of the brakes. If the bike moves down from only power added to the cranks you have pedal induced bob. If the chain is not pulling directly inline against the rear suspension Pivot (on a single pivot design) the bike will go down.
There have been some designs in MTB where the pivot was above the chain and the bike would actually go up when you accelerate with the brakes locked up. Moving the chain up or down on the front chainrings will impact the pivot alignment also.