Solid breeder blanket testing needs have been characterized in the FINESSE study. These testing needs have unique characteristics, especially in comparison to liquid breeder blankets. First, there are a large number of potential breeder materials and material variables. Secondly, the influence of radiation on the primary uncertainties is large, but the influence of geometry is not. Finally, much of the important functional behavior of the solid breeder is not described by classical equations, but rather the controlling phenomena must be quantified by experiments. Therefore, test conditions must match fusion reactor conditions as closely as possible. These factors suggest that a reasonable number of moderate volume test sites in a neutron environment are needed. The suitability of fission reactors and the major solid breeder experiments are considered here.