Test runs have been taking place on the Reading - Didcot section I believe. Although where exactly was it in the yard, and is any of it even electrified? Sorry haven't been over there lately so not sure.
It was in one of the DBC roads (that parallel the line from the station going round to Oxford) which is not wired. I'm surprised they are running these test trains from Didcot (with the need to diesel haul from the sidings to get under the wires) rather than from Reading Depot?