If you want to check that an engine+prop combination is delivering the correct power, there is only one wind and that is no wind.
Tailwind or headwind will lead to a change of prop blade AoA.
You also need ISA conditions (Q1013 and +15C), although there are easy corrections for that, which one has to do on a dyno test anyway (usually). For example I check for a takeoff fuel flow of 23.0 +/- 0.2 USG/hr, but this varies with the QNH.
I deleted the original thread myself because the usual suspects were, as usual, smelling an opportunity to take the micky and settle some hypothetical old scores, and if possible cause me hassle, and diverted the thread accordingly. I have nothing to hide.