Fabric Reinforced Cementitious Matrix (FRCM) composites represent an innovative and effective retrofitting solution for masonry structures. The use of FRCMs as an external retrofitting technique requires an insight knowledge of their mechanical behavior, failure modes and masonry-to-FRCM bond properties. A Round Robin Test (RRT) programme was launched by twelve Italian Universities, aimed at evaluating the effect of the shear test set-up parameters and at assessing the test variability. The experimental tests were performed on systems made of glass and steel fibers/cords applied onto masonry substrates. The results were carefully analyzed discussing failure modes, bond capacity, and slip statistical dispersion. Differences in the set-up, including the clamping method, textile impregnation, and instrumentation used for measuring the slip during the tests, were discussed in detail providing useful considerations and suggestions for reducing experimental scattering and obtaining reliable results.