We are testing our http server.  It is not obviously inappropriate to test the full string.  Especially in the Line to Long case, where we are testing that our specific error message is produced.  If you wish to argue that we should emit the standard message and only put the specific info in the body of the response, that would be a design change, and then we should probably test for *that*, since it would be a change from current behavior.  Personally I find the more-specific information being in the response code message to be helpful, but I haven't done enough web programming lately for my opinion to count for much :)

So, I do not think this issue needs to be separate from issue 12921.  The tests should be fixed as part of the enhancement being advocated there (and I certainly agree it should be *possible* to control the two messages separately, regardless of what we choose to do by default).