Fix connected_players on_shutdown (#14739)

games/devtest/mods/unittests/init.lua

@@ -186,6 +186,7 @@ dofile(modpath .. "/metadata.lua")
 dofile(modpath .. "/raycast.lua")
 dofile(modpath .. "/inventory.lua")
 dofile(modpath .. "/load_time.lua")
+dofile(modpath .. "/on_shutdown.lua")
 
 --------------
 

games/devtest/mods/unittests/on_shutdown.lua

@@ -0,0 +1,22 @@
+-- Test whether players still exist on shutdown
+local players = {}
+
+core.register_on_joinplayer(function(player)
+	players[player:get_player_name()] = true
+end)
+
+core.register_on_leaveplayer(function(player)
+	local name = player:get_player_name();
+	assert(players[name], "Unrecorded player join.")
+	players[name] = nil
+end)
+
+core.register_on_shutdown(function()
+	for _, player in pairs(core.get_connected_players()) do
+		local name = player:get_player_name()
+		assert(players[name], "Unrecorded player join or left too early.")
+		players[name] = nil
+	end
+
+	assert(not next(players), "Invalid connected players on shutdown.")
+end)