I'm INFP - first tested via a very long test on a program for
   MS-DOS back in 1993. Took it a few times more on the new
   Internet. Results were consistent. One day I challenged myself
   to mimic each type. Took about a year. The test is long and I
   had other stuff to do as well (like work). But one day, I
   succeeded. Now, i can't take the test anymore. Of course, it's
   only supposed to be once.