The Test Of This World Started Because Of Mistake By Adam (swS)?
If you want to understand the story of Adam (as) literally, it won’t make sense to you. “Human beings” before Adam (as) didn’t have the cognitive abilities which separate us from other animals. The generation of Adam (as) underwent cognitive revolution, so they sort of emerged from a garden of innocence and bliss. As to what occurred, it seems when human beings gained the capacity to plan/think about the future ( tree of eternal life as referenced in Quran ) and when they began to use the tools of nature for their own benefits ( Adam covering his body with leaves ). This cognitive revolution brought them from being in a state of childlike bliss to the stage of tests, suffering, trials, animosity, competition, material advancement, knowledge growth,moral conscious and the ability to communicate in a language.