I usually test INTP. Once I tested INFP. I find the introversion/Extroversion aspect to be universally misunderstood. I am not shy, which is probably why in the scientifically favored "Big 5" tests I show up on the extrovert spectrum. Anyway, I found the descriptions of INTP that I found on many test sites describe me to a tee.

INTP’s “focus on ideas and concepts rather than facts and details;” INTP’s “prefer to be spontaneous and flexible rather than planned and organized;” INTP “minds are complicated and active” — we “go to great mental lengths trying to devise ingenious solutions to interesting problems;” INTP’s are” typically non-traditional, and more likely to reason out their own individual way of doing things than to follow the crowd;” non-conformity is our natural state of being — it is not something we practice to shock others or make a statement. We “tend to share thoughts that are not fully developed, using others as a sounding board for ideas and theories in a debate against themselves rather than as actual conversation partners,” making us “appear unreliable, but in reality no one is more enthusiastic and capable of spotting a problem, drilling through the endless factors and details that encompass the issue and developing a unique and viable solution — just don’t expect punctual progress reports.”

“When INTP’s are particularly excited, the conversation can border on incoherence as they try to explain the daisy-chain of logical conclusions that led to the formation of their latest idea.” I often state my conclusions without connecting the dots.