I'm happy that this test is genuine, unlike the one that came with the car despite *many* areas of rot. The most worrying one was a big crack in the nearside chassis leg just behind where the suspension eyebolt goes through. It wasn't obvious because the cowboy who the previous owner had paid handsomely to maintain the car for her had covered it with a thick layer of underseal!
Last night I changed the oil, as you're supposed to do 500 miles after an engine rebuild. The oil was surprisingly black and there were lots of microscopic metal flakes in the bottom of the filter. That's presumably the high spots of the bearings and bores wearing smooth as the engine beds itself in.
The next thing I need to do is to clean up and paint all the areas where I've welded new metal in for the MOT (quite a lot of them!) because they are rusting very quickly indeed. I sprayed zinc primer on some of them but rust is starting to show through anyway.