Manually construct a parameterized module… the advantage here is multiple new functions and other static functions which do not take a module argument.

stub_mochiweb_request.erl

%% @author David Reid <dreid@mochimedia.com>
%% @copyright 2011 Mochi Media, Inc.

%% @doc Stub MochiWeb HTTP Request module implementation for testing.
-module(stub_mochiweb_request).

-record(stub_mochiweb_request, {options, headers, response_pid}).

%% Constructors and static method exports

-export([new/1, new/2, new/3]).
-export([response/0]).

%% Stub exports
-export([get/2]).
-export([parse_post/1]).
-export([get_header_value/2]).
-export([ok/2]).

%% Constructors and static method implementations

%% @spec new(list()) -> stub_mochiweb_request
%%
%%
new(Options) ->
    new(Options, []).

new(Options, Headers) ->
    new(Options, Headers, self()).

new(Options, Headers, ResponsePid) ->
    #stub_mochiweb_request{options=Options,
                           headers=Headers,
                           response_pid=ResponsePid}.

response() ->
    receive
        {mochiweb_response, Response} ->
            Response
    end.


%% Stub implementation

%% @spec get(field()) -> term()
%% @doc Return the internal representation of the given field.
%%      Field must be present in the Options proplist when
%%      this module was created by stub_mochiweb_request:new/1
get(Option, S) ->
    case lists:keyfind(Option, 1, S#stub_mochiweb_request.options) of
        {Option, Value} ->
            Value;
        false ->
            throw({unknown_option, Option})
    end.

parse_post(S) ->
    ?MODULE:get(post_variables, S).

get_header_value(Header, S) ->
    case lists:keyfind(Header, 1, S#stub_mochiweb_request.headers) of
        {Header, Value} ->
            Value;
        false ->
            undefined
    end.

ok(Response, S) ->
    S#stub_mochiweb_request.response_pid !
        {mochiweb_response, {ok, Response}},
    ok.