I think its important to have a tag that explicitly calls attention to code testing in the context of how do I increase coverage by... "Making calls to test invalid inputs without crashing my test class?", "design my class so that it tests all the if - else branches?", "generate data to test lines that catch exceptions without crashing the test class?", or "how do I get test coverage when invoking web services?", etc.
It sounds to me as though your issue is how to convey this through the meta-tag description so that it doesn't garner "do my work" questions? I can completely understand that perspective. Although I can't say how others use this site, it seems to me that meta-tags are often more of an afterthought than they are where someone begins when creating their posts. As for myself, I may have a few in mind, but tend to leave applying them until I'm finished creating a post.
People come here for a reason; because they have a problem they're looking for help with. Because humor is often lost in the written word, I want to be clear that I make the following statement with no intent to be disrespectful or dismissive of your Question Daniel. I simply don't believe we get many questions that result from someone finding a meta-tag then saying, "Oh, I should ask this question about this tag!" ;)
I genuinely applaud your efforts to clarify the use of this particular meta-tag. I'm encouraged to see that others care about creating community and are taking ownership of a place like this in a tiny corner of cyberspace. :) I've not seen that kind of community since I left CompuServe about a year after the AOL takeover destroyed the communities I'd been a part of that existed there (we're talking over 12 years ago).
To get back on topic... I strongly suspect the people who tend to be the caretakers of this forum are the ones who generally apply the appropriate meta-tags to posts more frequently than the members who use this place. There are many other meta-tags that clearly could benefit from having wiki tags written for them too. I look forward to the day those get written as well. :)
I think LaceySnr's suggested edit takes things somewhat in the right direction, yet it also "feels" a bit too limiting. At the same time, I have nothing better to suggest at this particular moment. Perhaps it's a matter of style. ;)