If I may ask how fast did you do 4th kyu I,m just a little apprehensive because I got winded really quickly.
My test was maybe 15-20 minutes long. My 3rd kyu was a little longer...maybe.(at least it felt longer) lol I don't think the kyu ranks are really long tests. At least they aren't in my school. At least in my school it isn't until 2nd kyu until they expect things to kick up the pace.
Who knows what your sensei might ask for in addition to the normal federation standard techniques.
Work on your endurance man. Take randori classes. Tests get more lively the higher the rank.