A tensile test method involving shape optimization of a thin, planar specimen has been developed. The purpose was to reduce the stress concentration in the transition zone between a straight-sided zone and a wider-end zone. Three designs of specimen, including an ISO standard design, were investigated based on finite element analyses. The technological applicability of two of the designs was tested on thin, planar cermets corresponding to the structurally supporting member of a planar anode-supported solid oxide fuel cell (SOFC). Application of optimized shapes appeared as a viable method. The maximum stress in the specimen was reduced to < 1.01 times the average stress. The fraction of invalid tests (i.e., specimens failing outside the gauge section) was reduced with the optimized shapes. The tested samples were cut into shape by laser as actual SOFC components. The cutting was seen to generate surface cracks that acted as the main failure initiator.