A method of identifying cell-internal defects: obtaining a circuit design of an integrated circuit, the circuit design including netlists of one or more cells coupled to one another; identifying the netlist corresponding to one of the one or more cells; injecting a defect to one of a plurality of circuit elements and one or more interconnects of the cell; retrieving a first current waveform at a location of the cell where the defect is injected by applying excitations to inputs of the cell; retrieving, without the defect injected, a second current waveform at the location of the cell by applying the same excitations to the inputs of the cell; and selectively annotating, based on the first current waveform and the second current waveform, an input/output table of the cell with the defect.