I had that problem using python. Cutting the last two digits of 10000 == 00 which through int("00") is 0. But you want 100 not 00. I just did a special case to catch that condition.

Why is the test expects n^0 being 1, whilst all other tests require n^0 being n?

This does not sound right. AFAIK this kata expects n^0 to be 1, also for n=0.
Maybe here you will find some hints how to search for error in your solution.