  Current generation of detectors using noble gases in liquid phase for direct
dark matter search and neutrino physics need large area photosensors. Silicon
based photo-detectors are innovative light collecting devices and represent a
successful technology in these research fields. The DarkSide collaboration
started a dedicated development and customization of SiPM technology for its
specific needs resulting in the design, production and assembly of large
surface modules of 20x20 cm^2 named Photo Detection Unit for the DarkSide-20k
experiment. Production of a large number of such devices, as needed to cover
about 20 m^2 of active surface inside the DarkSide-20k detector, requires a
robust testing and validation process. In order to match this requirement a
dedicated test facility for the photosensor test was designed and commissioned
at INFN-Naples laboratory. The first commissioning test was successfully
performed in 2021. Since then a number of testing campaigns were performed.
Detailed description of the facility is reported as well as results of some
tests.
