A test harness is basically an "application" that helps you do testing. It runs other software applications feeding data sets or sets of parameters to them and generally produces some sort of statistical output on how each program did over which data sets and parameter set. The trouble with them is that they have to flexible enough to be consistently useful and they need to be user friendly.
Someone else will have to answer the data bed question. I can guess but it would only be a guess so I will refrain.
The most exciting phrase to hear in science, the one that heralds the most discoveries, is not "Eureka!", but "That's funny..."
The most exciting phrase to hear in science, the one that heralds the most discoveries, is not Eureka!, but That's funny...