One of the better tests is temperature shock. Move the sample from
-40C to +40C and back again with enough time in between the moves for
the equipment to reach that temperature. If there are cold solder
joints then there is a very high probability that the solder will
actually break the connection. I used to do this testing for a living
and have seen more than a few failures this way. Even if contact is
not lost through the solder connection, visual inspection becomes much
easier as the bad connection will be more obvious. Using red or blue
light filters as you inspect the board can also be quite helpful.
Rob
