UNIT testing

White box, Black box, Component test; is your UUT realy stand-alone. Is the interface stand-alone? Most likely not. Is the interface automatable? ...sometimes the input or output from software that interfaces with hardware like a fingerprint scanner might actually require that you need real fingers to get good input data because a testing-layer that allows 'fake' input to get injected was never desighned in. I think that for a test engineer, the big headaches are around, have a specified and desighned enough tests, and should not be around things like. "Is it automatable, can I get it stand-alone and in the spotlight on it's own?". Reality is that integration testing will show you which unit tests you should have created, but never thought of. I think these are the ones where I want to kick myself, because a small failure has caused project hiccups.
I imagine there is a good book on this stuff, (unit test specification that is) and how you can go about nailing the beast down to produce quality in the right places early and easily. I must say I look forward to the next Symbian component testing project (probably some blue-tooth work) ,and I have learned a lot about unit-testing in 6 months. I look forward to Bluetooth, because it is something I know little about, and the possibilities there are really wide for some fun to be had.