Back home, in the 70's our favourite MOT tester was based in Moses Gate. between Bolton and Farnworth, his name was 'One-eyed Jack'. He'd say 'it's failed, rear light out'. I said, no it isn't look again. He'd cover his good eye up, look again and say. 'ok, pass!'.
What happened to these characters and their dodgy MOT's.......?
I'd strongly recommend a 5 litre brake flush, this is a technique where you pull lots of fluid through the system ensuring the old knackered fluid is truly changed.
Get a vacuum or forced bleed kit (the one I have works of a tyre deflated to 15psi pressurising an added reservoir to the master cylinder. You bleed 2 litres from the first (furthest) corner then the other rear and fronts a litre each. The difference is amazing and well worth the effort. Given that brake fluid is supposed to be replaced every 2 years I'd say most cars have never had it truly changed!