I got it right, but I wish the date wasn't April Fools day -- it adds a bit of "meta" distraction to the question.
Is it ha, ha fooled you if you pick it, or ha, ha should have picked this? Either way, an unwelcome distraction from an otherwise nice question.
Originally I had 28 December, but then thought "oh, people will expect a trick if I use that date" so changed it.
PS There was some sort of typo or word missing trom the explanation.
Yes, there was: "there" instead of "none", a very silly typo. I started with "if there isn't one of the tests which delivers true" or something similarly verbose and rotten style with a double negative like that, and decided to change it to "if none of the tests delivers true" and screwed up the edit.