Originally posted by: DarthEnder
Just to throw my 2 cents in, I can think of a couple reasons Itachi may have killed his clan.
...But thats not to say I'm not willing to accept the idea of "testing himself". Nevertheless I also believe, like some others here, that he is not referring to his power, he's referring to his ability to do anything to achieve a goal. Someone else said something to the effect of "I think a ninja would know what he would and would not do" but I disagree. It's like the saying goes, "you never really know what your capable of..." until you have to do it of course. Itachi knows that if he is capable of killing everyone in his family and his entire clan without remorse, then there is truly nothing he won't do to accomplish his goals, whatever they may be.