The fillet weld fracture test, or fillet weld break test, determines fillet weld soundness. This mechanical testing process examines the entire sample for root penetration. An arbor press, testing machine, or hammer places tension on the unwelded side of the sample. When the sample breaks or bends flat upon itself, an expert examines the weld for discontinuities or defects. The fracture test can reveal various embedded imperfections, including cracking, incomplete penetration, lack of fusion, porosity, and slag inclusions. This method often accompanies a macro etch test for more exhaustive detail about the weld quality.