MAJIS is part of the science payload of the ESA L-Class mission JUICE to be launched in 2022 with an arrival at Jupiter in 2030. MAJIS will perform imaging spectroscopy through two channels: VIS-NIR (0.50 µm - 2.35 µm) and IR (2.25 µm - 5.54 µm). The Royal Belgian Institute for Space Aeronomy (BIRA-IASB) and the Royal Observatory of Belgium (ROB) contribute to MAJIS with the characterization and calibration of the VIS-NIR Flight Model (FM) and Spare Model (SM) detectors, including the design, development, and validation of the setup, as well as the data processing pipeline. The FM and SM detectors are characterized under different illumination conditions (along four decades of dynamical range), temperature (125 K - 144 K), beam uniformities, exposure times, and/or data acquisition rates. In this paper, we describe the optical performances of the facility, which can be configurable for dark conditions, uniform light beam, and convergent beam with same focal ratio as MAJIS convergence optics. We provide a relative radiometry scale for the typical characterization measurements, as well as a fully characterized flux that will allow us to perform characterization measurements in an absolute radiometry scale, such as quantum efficiency (QE). In addition, we describe the thermal performances provided by the bench reaching different temperature scenarios, including the expected operating temperature of the detector at 132 K. The characterization facility was completed and subjected to validation tests in early 2020. The MAJIS VIS-NIR FM detector was delivered for its complete characterization in June 2020.