Don’t skimp on the test. Buy quietly from 5 different manufacturers the devices and test them min. 6 months, more likely 12-24 months. You can’t imagine how many solutions give up the ghost after only 6-12 months. Would be quite a pity if you then already ordered the next 500 pieces. Avoid too much financial risk here.
Where you should test them is quite clear: in the field. Never just at your warehouse or office. Put the IoT devices outside, in the sun, rain, snow or in the wet / cold factory, dry dusty warehouse, etc. You have to find out whether the devices really deliver what they promise and that too over a period of more than 6 months.
This time is well invested and ensures that you don’t lose 150.000€ – like a meanwhile very good and longtime customer of ours – because the devices broke down and he was left sitting on his money without further support or rework from the IoT manufacturer company.