ct_help.erl

-module(ct_help).

-export([mock/2]).
-export([load_mocks/1]).
-export([unload_mocks/1]).

-include_lib("common_test/include/ct.hrl").

mock(Mocks, Config) ->
    lists:foldl(fun do_mock/2, Config, Mocks).

load_mocks(Config) ->
    {Mocks, Config1} = mocks(Config), 
    [moka:load(M) || M <- Mocks],
    Config1.

unload_mocks(Config) ->
    {Mocks, Config1} = mocks(Config), 
    [moka:stop(M) || M <- Mocks],
    Config1.

%% ===================================================================
%% Private
%% ===================================================================

f(Fun) ->
    {arity, Arity} = erlang:fun_info(Fun, arity),
    f(Arity, Fun).

f(0, Fun) -> fun() -> {ok, Fun()} end;
f(1, Fun) -> fun(A) -> {ok, Fun(A)} end;
f(2, Fun) -> fun(A,B) -> {ok, Fun(A,B)} end;
f(3, Fun) -> fun(A,B,C) -> {ok, Fun(A,B,C)} end;
f(4, Fun) -> fun(A,B,C,D) -> {ok, Fun(A,B,C,D)} end;
f(5, Fun) -> fun(A,B,C,D,E) -> {ok, Fun(A,B,C,D,E)} end;
f(6, Fun) -> fun(A,B,C,D,E,F) -> {ok, Fun(A,B,C,D,E,F)} end;
f(7, Fun) -> fun(A,B,C,D,E,F,G) -> {ok, Fun(A,B,C,D,E,F,G)} end.

do_mock({_, []}, Config) ->
    Config;
do_mock({Mod, [{Fun, Behavior} | Rest]}, Config) ->
    {M, Config1} = get_mock(Mod, Config),
    replace(M, Fun, Behavior),
    do_mock({Mod, Rest}, Config1).

get_mock(Mod, Config) ->
    {Mocks, Config1} = mocks(Config),
    case dict:find(Mod, Mocks) of
        {ok, M} -> 
            {M, Config1};
        error -> 
            M = moka:start(Mod),
            Mocks1 = dict:store(Mod, M, Mocks),
            {M, lists:keyreplace(mocks, 1, Config1, {mocks, Mocks1})}
    end.

mocks(Config) ->
    case ?config(mocks, Config) of
        undefined ->
            Mocks = dict:new(),
            {Mocks, [{mocks, Mocks} | Config]};
        Mocks ->
            {Mocks, Config}
    end.

replace(M, {Mod, Fun}, Behavior) ->
    moka:replace(M, Mod, Fun, f(Behavior));
replace(M, Fun, Behavior) ->
    moka:replace(M, Fun, f(Behavior)).

foo_note.erl

-module(foo_note).

-export([find_note/2]).

find_note(User, Name) ->
    case foo_db:find([{type, note}, {user, User}, {name, Name}]) of
        {ok, Note} ->
            {ok, Note};
        Error ->
            Error
    end.

foo_SUITE.erl

-module(foo_SUITE).

-include_lib("common_test/include/ct.hrl").

-compile(export_all).

%% ===================================================================
%% Setup
%% ===================================================================

suite() ->
    [
        {timetrap, {seconds, 20}}, 
        {ct_hooks, []}
    ].

all() ->
    [
        find_note
    ].

groups() -> 
    [
    ].

init_per_suite(Config) ->
    Config.

end_per_suite(_Config) ->
    ok.

init_per_group(_Group, Config) ->
    Config.

end_per_group(_Group, Config) ->
    Config.

init_per_testcase(find_note, Config) ->
    Config1 = ct_help:mock([
            {foo_user, [
                    {{foo_db, find}, fun(Conds) -> 
                                {ok, {user, proplists:get_value(email, Conds)}}
                        end}
                ]},
            {foo_note, [
                    {{foo_db, find}, fun(_Conds) -> 
                                {error, not_found} 
                        end}
                ]}
        ], Config),
    ct_help:load_mocks(Config1);
init_per_testcase(_TestCase, Config) ->
    Config.

end_per_testcase(_TestCase, Config) ->
    ct_help:unload_mocks(Config),
    Config.

%% ===================================================================
%% Test cases
%% ===================================================================

find_note(_) ->
    {ok, User} = foo_user:find_user(<<"piyo@hoge.io">>),
    {error, not_found} = foo_note:find_note(User, <<"fuga">>).

foo_user.erl

-module(foo_user).

-export([find_user/1]).

find_user(Email) ->
    case foo_db:find([{type, user}, {email, Email}]) of
        {ok, User} ->
            {ok, User};
        Error ->
            Error
    end.