How much does a muslim have to do in order to prove themselves?

I asked a question that asked about ity in a sharia society. The majority of the answers told me that people become uals because Allah wants to test their faith. However, Allah, also know as the merciful, does not seem so merciful, if he inflicts ity onto a person living in a sharia state, even if they're abiding studiously to the sharia laws? Why must he go so far? You may or may not know, but since 1970s around 4000 uals have been executed in Iran. Why must allah be so cruel?