True speaking in tongues is speaking in other languages without knowing what you're speaking, from the bible it would be inspired things.
Anyway, the only way to know would be having someone if you were speaking in a language who would understand and translate.
Thanks to google translate, if you use a program from voice to text, and have it going into google translate, if you are speaking in tongues, the voice to text would spell most of it out correct and google translate would detect the language and translate it.
You would have no way of knowing if somebody doing this really knew the language and tricking you, but you can test it for your own self atleast.