Diversion material is particulate material used during wellbore treatment to temporarily seal a wellbore fluid passage such as a fracture. A method and apparatus for diversion material testing permits simulation of wellbore fracture parameters and testing thereof against a selected diversion material. The apparatus comprises: a fluid piping system including a fluid inlet end and a fluid outlet end; a fracture simulator chamber including a fracture-simulating outlet slot through a wall of the chamber, the fracture simulator chamber being releasably connectable to the fluid outlet end; a pump to pump fluid through the fluid piping system from the fluid inlet line to the fluid outlet end and into the fracture simulator chamber; a diversion material launch system connected in communication with the fluid piping system between the fluid inlet end and the fluid outlet line; and a pressure transducer in the fluid piping system to measure pressure in the fluid piping system.