The rule does not says that it must have a test case, it does says only that it is highly encouraged.
In case of code-trolling, in fact there is a clear specification of what constitutes a correct submission: It is a submission that do not do what the lazy OP asks, or do it in a really awful way. Since this specification is subjective, it is hard to write a test case. Yes, it is possible to be clear and subjective at the same time. So, it is still within this rule.
For the Y2K question, the situation is similar to code-trolling.
Hence, these questions can't be close for not following those rules, in fact they do.
It is true that all those questions are all subjective, so it would be hard to define any winning criteria other than popularity-contest. In fact, if it is a popularity contest, we do not even need a test case. I don't see that by having a subjective winning criteria as a bad thing, in fact I see it as a good thing.
I strong oppose to close those questions and I think that this would be harmful for this site. This site is all about programming for fun (no one would be squeezing bytes in a golfscript code or programming in befunge for anything else), so what we need to do is to keep the site fun. If you impose a one-size-fits-all rigid rule for everything, closing whatever does not fits there, the result will simply be the death of this site.
I am not saying that we do not need rules. I am saying that they should not be rigid. The rules serves for organizing the site in order that every user here could enjoy it in a fair way, its purpose is not to avoid anyone enjoying anything by making everything narrow and boring.