1. A system to produce a multi-user network game to be performed between a game server and a plurality of game clients via a network, the system comprising: a game production module configured to produce and debug the multi-user network game and a multi-user network execution environment; and an emulation module configured to emulate an execution of the multi-user network game by constructing a virtual network execution environment that comprises at least one server virtual machine and at least one client virtual machine, the at least one server virtual machine and the at least one client virtual machine being configured to execute the produced or debugged multi-user network game.