Add unit test to test various special characters in tag values

[replay]

This is a regression test to ensure that we continue supporting special characters in the tag values

Related #1216

Note: Github does not display all of it correctly. For some of the values to be shown correctly it is necessary to git fetch the commit and look at it locally.

[Dieterbe]

wouldn't it be simpler and more robust to iterate the ascii table (or a subrange of it) ?

[replay]

Yeah, I guess that would work. I wanted to test some UTF-8 as well. But i can replace the ASCII chars with some loop that just iterates over the table.

[replay]

This is now iterating over the ascii table and tests all characters except those on a short blacklist: 9d93f6d

[Dieterbe]

can't you just specify the actual characters like ':'

[replay]

yes, that works too: 42c75fa

[Dieterbe]

seems like % 128 is redundant given the check below

[Dieterbe]

maybe change to for isBlacklisted(rune(firstChar)) && i < 128 {

[Dieterbe]

what is the purpose of setting these very low lastUpdate values?
seems it has nothing to do with what is being tested, and i would emit this from the testCase types

[Dieterbe]

also, having all these predeclared id's complicates things needlessly. just generate them as you need them

[Dieterbe]

I'm not sure how useful this PR is.
It basically confirms that if in Go you create a string using any ascii char or any unicode characters, and you copy that string, that equality between them works.
This is something the runtime provides and not something we should be dedicating 100 lines of code for, or even test at all, I think.

It seems more useful to think about where special characters may be problematic and either test those or analyze and document them.
E.g. when:

• parsing incoming carbon or MetricData input
• when generating messagepack and json responses. (wether intra-cluster or to clients) will characters that have a meaning in json be roperly escaped? This could use a unit test for our custom json encoder. For msgp we use a 3rd party library so we should look at the docs and/or contribute unit tests to the msgp project.
• when parsing user queries that come in over the http api.

[Dieterbe]

@replay what's the status of this?

[replay]

@Dieterbe Ok, in that case we can close this PR and I'll make another one with unit tests which test via the APIs and the MetricData input, instead of directly testing on the index interface.