The optimal development and management of a geothermal resource requires a knowledge of the hydrological characteristics of the reservoir. Reservoir engineering analysis techniques for permeable aquifers have been undergoing development for several decades but little attention has been paid to fracture-dominated systems. A program to test the ability of Huff-Puff tests to help characterize a fracture-dominated reservoir is presented. Several series of these injection (Huff)-backflow (Puff) tests were conducted at the Raft River KGRA in Southern Idaho. These test series are described and preliminary results and interpretations are discussed.