  The recently commissioned Dark Energy Spectroscopic Instrument (DESI) will
measure the expansion history of the Universe using the Baryon Acoustic
Oscillation technique. The spectra of 35 million galaxies and quasars over
14000 sqdeg will be measured during the life of the experiment. A new prime
focus corrector for the KPNO Mayall telescope delivers light to 5000 fiber
optic positioners. The fibers in turn feed ten broad-band spectrographs. A
consortium of Aix-Marseille University (AMU) and CNRS laboratories (LAM, OHP
and CPPM) together with LPNHE (CNRS, IN2P3, Sorbonne Universit\'e and
Universit\'e de Paris) and the WINLIGHT Systems company based in Pertuis
(France), were in charge of integrating and validating the performance
requirements of the ten full spectrographs, equipped with their cryostats,
shutters and other mechanisms. We present a summary of our activity which
allowed an efficient validation of the systems in a short-time schedule. We
detail the main results. We emphasize the benefits of our approach and also its
limitations.
