Drew wrote "not everyone is naturally talented at aikido and if testing was done on technique ability alone there would be far less aikidoka then there is now."
I suppose this is where I was going with my original question. It doesn't seem to me that testing can be based on technique alone: it must be an objective standard relating to actual techniques but a subjective standard as to whether the student testing is performing the technique at a level appropriate to them as an individual.
Small thread but interesting comments.
I also do not beleive it is based on technique alone, if you look at a BAF (british aikido federation) grading result form the sections are
Knowledge of Technique
Flow and Flexibility
Maai & Zanshin
Manner and Attitude