A method of testing electronic assemblies including singulated TSV die attached to a ML package substrate, on a substrate carrier. The substrate carrier includes through-holes for allowing probe contact to the BGA substrate pads on a bottomside of the package substrate that are coupled to the frontside of the TSVs. Contactable TSV tips on the bottomside of the TSV die are contacted with a topside coupler that includes a pattern of coupling terminals that matches a layout of at least a portion of the TSV tips or pads coupled to the TSV tips. The topside coupler electrically connects pairs of coupling terminals to provide a plurality of TSV loop back paths. The BGA substrate pads are contacted with a plurality of probes tips that extend through the through-holes to couple to the frontside of the TSVs. Electrical testing is performed across the electronic assembly to obtain at least one test parameter.