What's the best way to test the leaderboard
As far as I know, there is a local cache, thus, the Get Leaderboard Stat chip should give you the correct result right after it has been set with the Set Leadboard Stat chip (I'm not sure whether it is in the next tick, but it might be). The synchronization with the server is only for the leaderboard display and for the case that a player goes to another instance of the same room or a subroom. Thus, you should always use the Get Leaderboard Stat for debugging and wait a few minutes in cases that involve room changes.