It was totally nonsense when LeaveBuster caught a player testing his champion in Practice Tool
In LoL, Practice Tool was created by Riot Games in order to let their players make some experiments on a champion bought recently or give new builds a try. Besides, the Fast Forward function was also added to help players to own items from Magical Footwear or Perfect Timing as soon as possible. And for sure, when it is activated, your champion will not be able to move or do anything.
This Tool has worked normally since it came to live servers until the LeaveBuster system busted a player just because it detected his behavior of standing stably in a while. Specifically, a player whose Reddit account named u/BBQMasterDad entered the Practice Tool, use Fast Forward, and tried killing hundreds of minions by Nunu&Willump’s R. After that, he suddenly received a 15-min ban for leaving the game(?) and the whole community said that that system of Riot was completely a joke.
The reason for this is that probably, the LeaveBuster system also gives an eye on players’ behaviors, even when they are playing in Practice Tool. As a result, when Fast Forward is activated, which means your champion cannot move for a while, that system will accuse you of leaving the game and apply a temporary ban. (Is Riot slapping themselves???).
So as to avoid hilarious situations like this, Riot Games actually need to fix their system carefully. This system should detect leaving behaviors in every game mode apart from Practice to let players test anything they want without worrying about getting banned.