I have a personal annoyance with most of these type-measuring sites, which is their inflexibility with punctuation.
I normally type two spaces after a sentence, and it's been deeply wired into my muscle memory since 1983 (when I took my 8th-grade typing class). The sites that I've used count a double-space as an error, and require you to go back and fix the error before moving on.
The same thing with dashes. I use publishing convention, which is two dashes for an em-dash with a space on either side. keyhero, for instance, uses just a single dash, occasionally with no surrounding spaces, occasionally with one. Either way, if you get it wrong, you need to go back and fix it.
There should be more flexibility in their engines for evaluating typographic mistakes, instead of mere character-by-character correctness. Such limitations have me constantly self-monitoring, just to make sure that I'm hitting their punctuation absolutely correctly, in spite of what my muscle memory wants to do.
Just now, I managed to score a 103.42 WPM with 98.48% accuracy. I wonder what I would get if I wasn't constantly scanning for punctuation.