Ah yes.... I also did a small board with eight buffered LEDs . The inputs are connected via a 680K resistor (to load the DUT as little as possible) and and diode to level-shift the active level up a bit.

The gain of the 2n3904's is enough to drive LEDs decently bright with the minuscule current that passes thru the 680K resistor at 5 volts (minus the diode and transistor junction drops).