The only flight test I ever failed in my long career was the initial Pommy I.R. way back in 1973.
I had been flogging around the Pacific Islands in aircraft that only had two ADFs. Having done literally hundreds of NDB approaches, but with no experience of the VOR or ILS, when I got to Blighty and had to pay lots of pounds sterling to hire a Twin Comanche, I told the school that all I wanted to do was practice VOR and ILS work - I was already the World's Greatest NDB Approach Man.
Come the big test day and the CAA Examiner rocks up in his black uniform with gold braid running half way up both sleeves. Complete with regulatory handlebar moustache he was a formidable figure. I got the failure warning spiel that Tee Emm has succinctly described.
We get in the Tin Bomb and off we go, with me checking for ice every five minutes as prescribed (even though it was clear weather) and I nail the VOR, holding pattern and ILS. But back on the ground his first words are: " I regret to inform you that you have failed because your NDB tracking was 7 degrees off for 20 seconds on the inbound leg and you are only permitted five degrees for 15 seconds" (or some-such). Never mind it was a pathetic low-powered NDB and the Tin Bomb's equipment was hardly state-of-the art, I just had to suck it up. Because the rules had been laid down and I had accepted them.
Now whether there was some collusion between the school and the CAA man to bring this Wild Colonial Boy into line, I dunno, but it was a good lesson in humility for me. Don't present yourself for a test until you are ready and when you do, accept the rules.