Performance of triple-GEM detectors for the CMS Phase-2 upgrade measured in test beam

Triple-GEM detectors for the GE2/1 and ME0 stations of the endcap muon system for the Phase-2 upgrade of the CMS experiment have been operated in a test beam to measure their efficiency and spatial resolution, together with a high spatial resolution triple-GEM tracker. A production module of GE2/1 detectors and a prototype ME0 detector show excellent local efficiency. A prototype detector with GEM foils employing \it random hole sectorization \rm showed significant reduction of dead areas. The spatial resolution of the tracker has been measured and found close to the expected value of 75 $\mu$m.