The Schulze ring shear tester allows measurement of yield loci for bulk granular solids and of the friction between the solids and the container wall material. These measurements are required inputs in a systematic design method for hoppers. The measurements are subject to test-to-test variations caused by the combined effects of several factors, such as cell filling technique, sampling technique, particle size and shape distribution of the loaded sample and cell size relative to the particle size. One difficulty for the experimenter is to decide which factors are most important in the shear test outcome. In this paper, we validate Discrete Element Model (DEM) simulation parameters with physical measurements of the JSC-1A lunar soil simulant, and inform about the relative impact of the various parameters to the shear test outcome. Specific tests will include sensitivity studies using DEM simulations that probe the effects of particle-to-cell size ratio, particle size distribution, particle shape, shear modulus and inter-particle adhesion and friction on shear failure.