The psychological tests of ISSB are much like that of taken by FPSC. But there is a difference. in iSSB the caliber of the candidates is very low while for the CSS they need much more mature personality. So all those those candidates who have been through ISSB take this thing in your consideration too.
In general Psychological tests are the test of the Persona and the shadow of one's personality. they wil assess as to what a persons pretends and what he actually is from inside. means what he says and what he believes. they will judge the difference of opinions if there is any in one's personality. And most importantly mantle trends of a person and their suitability for the opted group.
So the simplest way to go through the test is to behave in the most natural way. Do't pretend to be someone that you are actually not. So the formula is BE NORMAL AND NATURAL. and mature. simple is this.