Posted on Thursday, 9th October 2008 by charpi
In my previous post, I described a way to mock module by replacing
them. Today, I’ll post a version closer to other mock
library. Basically, I create on mock module on the fly and forward all
calls to a process. You can tell to this process how to answer for
each calls.
Here is the test :
%%% Copyright (c) 2008 Nicolas Charpentier %%% All rights reserved. -module(mock_test). -export([test /0]). test () -> lazy_way () , dynamic_way (), ok. lazy_way () -> "i'm the production code" = my_module: who(), mock: replace_module (my_module, my_mock_module), "I'm the mocked code" = my_module: who (), mock: uninstall (my_module), "i'm the production code" = my_module: who (), ok. dynamic_way () -> "i'm the production code" = my_module: who (), {pong,host} = my_module: ping (host), mock: start (), mock: add_module(my_module), mock: set_answer (my_module, who, "I'm the mocked code"), "I'm the mocked code" = my_module: who (), mock: set_answer (my_module, who, "Oops did it wrong"), "Oops did it wrong" = my_module: who (), [{my_module, who, []}, {my_module, who, []}] = mock: calls (), [] = mock: calls (), case catch my_module: ping(host) of error_no_response -> ok; Other -> exit({unexepected_mock_response, Other}) end, mock: set_answer (my_module, ping, {pang, mock_host}), {pang, mock_host} = my_module: ping(last_host), [{my_module, ping, [host]}, {my_module, ping, [last_host]}] = mock: calls (), mock: uninstall (my_module), "i'm the production code" = my_module: who (), {pong,host} = my_module: ping (host), ok.
and the implementation
%%% Copyright (c) 2008 Nicolas Charpentier %%% All rights reserved. -module(mock). -export([replace_module /2]). -export([uninstall /1]). -export([start /0]). -export([add_module /1]). -export([set_answer /3]). -export([calls /0]). replace_module (Module, Mock_module) -> uninstall (Module), {ok, Binary} = file: read_file (code: which (Mock_module)), File_name = atom_to_list (Module) ++ ".erl", code: load_binary(Module, File_name, Binary), ok. uninstall (Module) -> code: purge (Module), code: delete (Module). start () -> Pid = spawn_link (fun () -> mocker ([],[]) end), register(mocker, Pid), ok. add_module (Module) -> Forms = forms (Module), uninstall (Module), {ok, _, Binary} = compile: forms(Forms, [report]), code: load_binary (Module, "foo.erl", Binary), ok. set_answer (Module, Function, Answer) -> mocker ! {set_answer, Module, Function, Answer}, ok. calls () -> mocker ! {self(), calls}, receive {calls, Calls} -> Calls end. forms (Module) -> Exported_functions = find_exported_functions (Module), Fun = fun (F) -> function_to_form (Module, F) end, Functions_forms = [Fun(F) || F <- Exported_functions], [{attribute,1,module,Module}, {attribute,3,export,Exported_functions}] ++ Functions_forms ++ [ {function,16,wait_response,0, [{clause,16,[],[], [{'receive',20, [{clause,20, [{tuple,20,[{atom,20,response},{atom, 20, undefined}]}], [], [{call,20, {atom,20,throw}, [{atom,20,error_no_response}]}]}, {clause,20, [{tuple,20,[{atom,20,response},{var,20,'Response'}]}], [], [{var,19,'Response'}]} ]}]}]}, {eof,23}]. function_to_form (Module, {Function, Arity}) -> Parameters = parameters (Arity), Parameters_cons = parameters_cons (Arity), {function,5,Function,Arity, [{clause,5,Parameters,[], [{op,6,'!', {atom,6,mocker}, {tuple,6, [{call,6,{atom,6,self},[]}, {atom,6,forward}, {atom,6,Module}, {atom,6,Function}, Parameters_cons]}}, {call,8,{atom,8,wait_response},[]} ]}]}. parameters (0) -> []; parameters (N) -> Seq = lists: seq (1,N), F = fun (I) -> String = lists:flatten (io_lib: format ("Var~p",[I])), list_to_atom(String) end, [{var, 6, F(I)} || I <- Seq]. parameters_cons (N) -> parameter_list_form (parameters (N)). put_parameter_in_call (Parameters) -> list_to_tuple (transform_list_to_cons (Parameters)). transform_list_to_cons ([]) -> [nil, 6]; transform_list_to_cons ([H|T]) -> [cons, 6, H, put_parameter_in_call (T)]. parameter_list_form ([]) -> {nil,6}; parameter_list_form (Variable_forms) -> put_parameter_in_call (Variable_forms). find_exported_functions (Module) -> Module_info = Module: module_info (), All_exported = proplists: get_value (exports, Module_info), lists: filter (fun ({module_info,_}) -> false; (_) -> true end, All_exported). mocker (Modules, Calls) -> receive {From, calls} -> From ! {calls,lists: reverse (Calls)}, mocker (Modules, []); {set_answer, Module, Function, Answer} -> New_modules = proplists: delete ({Module, Function}, Modules), mocker ([{{Module, Function}, Answer}|New_modules], Calls); {From, forward, Module, Function, Args} -> Response = proplists: get_value ({Module,Function}, Modules), From ! {response, Response}, mocker (Modules, [{Module, Function, Args}|Calls]) end.
Tags: erlang, mock object
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