@vahpor yes you can run 2 COBs for testing. Just make sure the connections are not "intermittent" or the voltage pressure could pop a COB. I blew a CXA3070 on an HLG-185H-1050B (191V max). It worked fine until I moved the test rig around a bit while powered up and this caused an intermittent connection. The driver tried to bump up the voltage because it was trying to figure out what was going on and the overvoltage partially destroyed the COB.
Another lesson I learned while testing an HLG-185H-700B (286V max) If you power up the driver with no load and then switch it off, it will take 20-30 seconds to power down on the DC side. It is capable of delivering quite strong zap