diff --git a/src/ggs_gamevm.erl b/src/ggs_gamevm.erl
index 1a8f547..15cbb64 100644
--- a/src/ggs_gamevm.erl
+++ b/src/ggs_gamevm.erl
@@ -1,24 +1,34 @@
--module(ggs_gamevm).
--export([start_link/0, define/2, user_command/4]).
 %% @doc This module is responsible for running the game VM:s. You can issue
 %% commands to a vm using this module.
 
+-module(ggs_gamevm).
+-behaviour(gen_server).
+
+%% gen_server callbacks
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
+         terminate/2, code_change/3]).
+
+-record(state, { port, table } ).
+
+%% API
+-export([start_link/1, define/2, user_command/4, stop/1, call_js/2]).
+
+-include_lib("eunit/include/eunit.hrl").
+
+
+%% ----------------------------------------------------------------------
+% API implementation
+
 %% @doc Create a new VM process. The process ID is returned and can be used
 %% with for example the define method of this module.
-start_link() ->  
+start_link(Table) ->
     erlang_js:start(), %% @TODO: should only be done once
-    PortPid = spawn_link(   fun() ->
-                                process_flag(trap_exit, true),
-                                {ok, Port} = js_driver:new(),
-                                js:define(Port, <<"function userCommand(user, command, args){return 'Hello world';}">>),  
-                                loop(Port)
-                            end ),
-    PortPid. 
+    {ok, Pid} = gen_server:start_link(?MODULE, [Table], []),
+    Pid.
 
 %% @doc Define some new code on the specified VM, returns the atom ok.
 define(GameVM, SourceCode) ->
-    GameVM ! {define,SourceCode},
-    ok.
+    gen_server:cast(GameVM, {define, SourceCode}).
 
 %% @doc Execute a user command on the specified VM. This function is
 %% asynchronous, and returns ok.
@@ -28,23 +38,81 @@ define(GameVM, SourceCode) ->
 %%      Command = a game command to run
 %%      Args    = arguments for the Command parameter
 user_command(GameVM, Player, Command, Args) ->
-    Ref = make_ref(),
-    GameVM ! {user_command, Player, Command, Args, self(), Ref},
+    gen_server:cast(GameVM, {user_command, Player, Command, Args}).
+
+%% @private
+% only for tests
+call_js(GameVM, SourceCode) ->
+    gen_server:call(GameVM, {eval, SourceCode}).
+    
+% @doc stops the gamevm process
+stop(GameVM) ->
+    gen_server:cast(GameVM, stop).
+
+
+%% ----------------------------------------------------------------------
+
+%% @private
+init([Table]) ->
+    process_flag(trap_exit, true),
+    {ok, Port} = js_driver:new(),
+    %% @TODO: add here default JS API instead
+    {ok, #state { port = Port, table = Table }}.
+
+%% private
+% only needed for the tests
+handle_call({eval, SourceCode}, _From, #state { port = Port } = State) ->
+    {ok, Ret} = js:eval(Port, list_to_binary(SourceCode)),
+    {reply, Ret, State}.
+
+%% @private    
+handle_cast({define, SourceCode}, #state { port = Port } = State) ->
+    ok = js:define(Port, list_to_binary(SourceCode)),
+    {noreply, State};
+handle_cast({user_command, Player, Command, Args}, #state { port = Port } = State) ->
+    Arguments = string:sub(string:join([Player, Command, Args], ","), "'", "\'"),
+    Js = list_to_binary(string:concat(string:concat("userCommand(", Arguments), ");")),
+    js_driver:define_js(Port, Js),
+    {noreply, State};
+handle_cast(stop, State) ->
+    {stop, normal, State};
+handle_cast(Msg, S) ->
+    error_logger:error_report([unknown_msg, Msg]),
+    {noreply, S}.
+
+%% @private
+handle_info(Msg, S) ->
+    error_logger:error_report([unknown_msg, Msg]),
+    {noreply, S}.
+
+%% @private
+terminate(_Reason, _State) ->
     ok.
 
-%% Helper functions
+%% @private
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
 
-loop(Port) ->
-    receive
-        {define, SourceCode} ->
-            ok = js:define(Port, list_to_binary(SourceCode)),
-            loop(Port); 
-        {user_command, User, Command, Args, From, Ref} -> 
-            {ok, Ret} = js:call(Port, <<"userCommand">>, 
-                                    [   list_to_binary(User),
-                                        list_to_binary(Command),
-                                        list_to_binary(Args)
-                                    ]),
-            From ! {Ref, Ret},
-            loop(Port)
-    end.
+%% ----------------------------------------------------------------------
+% Tests
+
+start_link_test() ->
+    erlang_js:start(), %% @TODO: should only be done once
+	GameVM = start_link(test_table),
+	?assertNot(GameVM =:= undefined).
+	
+define_test() ->
+    GameVM = start_link(test_table),
+    define(GameVM, "function hello(test) { return test; }"),
+    ?assertMatch(<<"jeena">>, gen_server:call(GameVM, {eval, "hello('jeena')"})).
+    
+stop_test() ->
+	GameVM = start_link(test_table),
+	ok = stop(GameVM).
+
+user_command_test() ->
+    GameVM = start_link(test_table),
+    define(GameVM, "var t = '';\nfunction userCommand(user, command, args) { t = user + command + args; }\n"),
+    user_command(GameVM, "'jeena'", "'thecommand'", "'theargs'"),
+    ?assertMatch(<<"jeenathecommandtheargs">>, gen_server:call(GameVM, {eval, "t;"})).
+