^Along those lines, we used to test several audio and video parametrics with the DUT in an 'oven,' (a temperature & humidity controlled small chamber about the size of an actual oven, with small holes in the side to allow cabling in and out) in which we could vary the temperature and humidity. We could test over a 100 degree temp range with humidity from nearly 0% up to near 100%.
We had requirements on products to be *functional* over certain very wide temp/humidity ranges, and other requirements that the product continued to meet parametric specs (freq resp, thd, snr, etc) over narrower ranges. For example (just making up numbers), product had to be functional from 40 deg F to 120 deg F, and had to meet all parametric specs while operating from 60 deg F to 90 deg F.
Of course, if the chamber temperature was set to x degrees, the actual temperature of some components on the board would be higher than x.