The listing should provide details of any test procedures followed, or if the item is being offered as untested.Nearly all of what I sell is tested to the best of my ability - but please bear in mind that I don't work for the manufacturer and I don't have access to a factory test rig.  So my definition of tested is that I power up the device and check for basic functionality - for example that it passes audio cleanly, that the LEDs flash as they should and that the meters move etc.In the case of items that have a large number of additional connections for external control logic etc then it wouldn't be cost effective to make up a custom tester and cabling set just to sell one item so unless there's reason to doubt that these functions are working, it's unlikely that they would have been tested by me.The approach above works well in practice - I have a return rate of well below 1% on tested items (and actually 90% of those re-test as perfectly OK).  So the odds of anything being amiss are low but not zero, a point that I would ask you to bear in mind if you are ordering internationally.