3 threads just today suggested that the spark be tested as part of
diagnosing a non-start.

Actually the traditional way to do this involves having a kid brother
or possibly your mother-in-law hold the plug wire.  Failing that, I
use one of these:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=4424

Pretty handy really.  They go on sale often for about 2 bucks.  Try it
one time when all is well to get an idea what a strong spark looks
like.