Really, if your brake fluid is the original or hasn't been changed for some time, accept that your tester was doing you a favour and have it changed - the cost is trivial compared to a potential accident or loss of life.....
Ron.
Spot on , well said that man
even if it's clean looking in the reservoir, who knows what it's like in the calipers,plus it absorbs moisture ,replacing it on a regular basis based on mileage AND age is good practice.
As for the NT (mot tester) he has inspected the brakes,felt pedal travel, brake tested on the rollers (so knows what the brakes are like) and can compare from experience good and bad brakes .
even if it is the cars first MOT , that is 3 year old brake fluid
I think tyres and brakes are pretty important and just meeting the minimum requirements at MOT time warrants at least an advisory , because some people get their MOT certificate and do NO maintenance to their car for another 12 months (next MOT )