The rig that occurred to me was to make up an extended cable, so that the bits did not have to be put together to be tested. It might be possible to cut the stranded cable in places and then solder in extensions of fine insulated wire with heat shrink sleeving covering the individual solder joints. Obviously this cable could not then be used for flight. I don't know if the original strands of wire will take solder. I did not try this.
Aside from any soldering difficulties I do not know if the cable length is critical i.e. if signal transit times are critical/sensitive. If the idea works it jmight be wise to embed the back of the cable's connectors in some sort of support. I worry about flexing of the individual wires in this area fatiguing them
