Type confusion.

This sounds kind of mean, but some people just are not good at self assessment. I actually have a friend who did the exact same thing. Tested as ISTP, few months later, ENFP. I still can't sort him out because his behavior is very hard to read because to him everything is a joke.

 

1) Self-assessment is inherently biased and people often perceive themselves in a very different way than they -actually- are.

2)Online MBTI tests are utter, useless crap, and no semblance of accuracy should be expected from them. The simple ones that just measure the one letter axis and have one dimensional, stereotyped questions, not to mention that the letter axis, or the cognitive functions aren't something that can be quantified like these tests attempt to do. The cognitive test ones are just useful as an introduction to the concept of functions, or an indication, but shouldn't be seen as set in stone.

3) A lot of people notice their results are dependent on mood and other external factors, and that's because they actually are. The test measures nothing but your self-aware, or idolized preferences at the time.

In conclusion - Online MBTI tests, massive testing fail.

 

It is seriously tough to type someone if they are under a lot of stress or have developed serious complexes, not saying either applies to him but it is something to keep an eye out for.