fix int overflow in test
fix int overflow in test

alesiong/CUHKSZLib,Yexiaoxing/CUHKSZLib,Yexiaoxing/CUHKSZLib,cuhkshenzhen/CUHKSZLib,Yexiaoxing/CUHKSZLib,cuhkshenzhen/CUHKSZLib,alesiong/CUHKSZLib,alesiong/CUHKSZLib,cuhkshenzhen/CUHKSZLib