Do any of these tests have validity? I have answered in what I personally believe in, as opposed to how I want government to run.
They're all very subjective, if that's what you mean. Where someone will fall is entirely dependent on the questions you ask, how many you ask, and how much you weight each response. I had one (very libertarian-biased) peg me at -6,-4-ish yesterday, while this one put me at -9.88,-8.05. Both slapped more-or-less the same labels on the quadrants. These're by their nature arbitrary - the only thing they'll tell you is very roughly where you fall according to their arbitrary measure. That this one give results to two decimal places make it seem comically precise, when it's anything but. The only conclusions I'd be willing to draw from them are along the lines of "I scored lower/higher on this single measure than you on this given test" or suchlike, and even then I'd not put too much faith in it.
The more I think about how this is structured, the less faith I have in it to tell you anything meaningful, except at the extremes, and even that could be misleading. The choice of wording on a question could easily cause one person to "Agree Strongly" and another to merely "Agree", even though they have roughly identical outlooks on the matter at hand. I suppose an individual score could be remarked upon with reasonable confidence if it was highly polar, but I'd say comparisons are bound to be muddled and misleading.