I can only answer regarding the CVSA test I was given last week
(which gave inaccurate results), but it was using the laptop setup
which I gather is used by almost all the police departments and
such that use the junk.

I was "tested" using what appeared to be a maybe $5 Radio Shack
quality clip-on condenser mike, perhaps 1 inch across, with 
attached PVC cable of similarly junk quality.   It was a crummy little
oval of beige plastic, and output from it was low enough that the
"tester" was having me practically shout into it.  I ended up having
to take it off my lapel and hold it in front of my mouth.

The mike was probably somewhat directional.  No precautions were
taken for background noise or physical stability of the mike, so that
low frequency  noise in the room (the window was open, facing a
parking lot) might have easily caused the mic to vibrate, it only 
weighed a couple of grams.

Despite a grilling of over 2 hours, and 2 passes through the list of
questions, it missed things which it might have caught, and said
that I was lying about areas where I have never in my life done a
single friggin' thing.  I can't figure out from this which of the
DoD's tests were correct -- that its accuracy is 38% or 49%.  But
if my experience is typical, I don't see any point in wasting money
on a better microphone.  It's snake oil.  The only positive thing I
can say about the experience was that my new boss was enlightened
enough to hire me over the objections of the agency which administered
the "test."

I did recommend that they consider upgrading to a pressure-zone
electret or the like, so that people wouldn't have to shout into the
damned thing, but the blank look I got in response let me know
that they had no clue what I was talking about.