This paper presents the experimental validation of a novel fault-tolerant electronic logic design conducted by an automated mixed-signal fault injection procedure. The design under evaluation relies upon a novel redundant design strategy intended to provide fault discrimination and selective fault masking embedded within a functional CMOS NAND gate. The traditional logic layout is modified to include fault detection and reporting at an extremely fine-grained design level with 2x overhead as opposed to the traditional 4x overhead. The fault injection test bench procedure requires automated fault injection, programmable fault load conditions and combined analogue/digital domain verification. The device under test is implemented using discrete n- and p-FETs arranged as a modular test board together with automated fault injection and test lines. The fault response is measured and confirms the predicted intrinsic fault rate of 25% with a successful 100% masking of suck low-faults and precise identification of stuck-high via IDDQ trigger. The test procedure is shown to be extensible towards more complex logic unit designs and for evaluation of multiple simultaneous faults.