Testing PDNs is a tough test because of extremely low impedances here. Tests leads from your injector to the board are simply a no-no. Another challenge is that modern FPGAs draw 10s of amps at *very* low voltages. To make this move, you need to inject several Amps right at the DUT, asking for a very compact, solder-in solution for the injector and the same for the probe. This smells like copper-base PCBs, very modern switching MOSFETs in small cases, super-compact, all SMD designs, and so on. A funny challenge, but certainly not easy. An alternative for directly soldering the injector and the probes into the circuit is ultra-low inductance coax.