An introduction to Meck, the mocking framework for Erlang, given at the Erlang User Group meeting on the 5th of November in Berlin.

1. MECK

2. ADAM LINDBERG
@eproxus
hello@alind.io

3. 1000 lines of code

4. 18 contributors

5. 2 years old

6. meck:new(atom()).

7. 1> meck:new(foo, [non_strict]).
ok
2> foo:module_info(exports).
[{module_info,0},{module_info,1}]

8. 3> meck:expect(foo, bar, 0, baz).
ok
4> foo:bar().
baz

9. 5> meck:expect(foo, bar, fun() -> baz end).
ok
6> foo:bar().
baz

10. 6> meck:expect(foo, bar, [1, true], baz).
ok
7> foo:bar(1, true).
baz
8> foo:bar(1, false).
** exception error: no function clause
matching test:bar(1,false)

11. 11> meck:expect(foo, bar, [1, '_'], baz).
ok
12> foo:bar(1,true).
baz
13> foo:bar(1,false).
baz

12. 28> meck:expect(foo, bar, [{[1, true], baz},
{[1, false], qux}]).
ok
29> foo:bar(1,true).
baz
30> foo:bar(1,false).
qux

13. [func_clause_spec()]

14. [func_clause_spec()]

15. [{args_spec(), ret_spec()}]

16. [{[any() | '_'], ret_spec()}]

17. [{[any() | '_'], ret_spec()}]

18. [{[any() | '_'], ret_spec()}]
any() | meck:val(any())
meck:loop([any()])
meck:seq([any()])
meck:raise(Class, Reason)

19. meck:expect(foo, bar, [
{[read], meck:seq([a, b, c, eof])},
{['_'], meck:loop([1, 2, 3])}
])

20. 79> [foo:bar(read) || _ <- lists:seq(1, 5)].
[1,2,3,eof,eof]
80> [foo:bar(write) || _ <- lists:seq(1, 5)].
[1,2,3,1,2]

21. 32> meck:expect(foo, bar,
fun() ->
meck:exception(error, epic_fail)
end).
ok
33> foo:bar().
** exception error: epic_fail
in function foo:bar/0

22. 9> meck:new(string, [passthrough, no_link,
unstick]).
ok
10> string:len("meck").
4

23. ?assert(meck:validate(foo)).

24. ?assert(meck:called(foo, bar, [1, '_'])).

25. ?assertEqual(4,
meck:num_calls(foo, bar, [1, '_'])).

26. 81> meck:history(foo).
[{<0.153.0>,{foo,bar,[]},baz},
{<0.153.0>,{foo,bar,[]},baz},
{<0.153.0>,{foo,bar,[1,true]},baz},
{<0.153.0>,{foo,bar,[1,false]},
error,function_clause,
[{foo,bar,[1,false]},...]},
{<0.167.0>,{foo,bar,[1,true]},baz},
{<0.167.0>,{foo,bar,[1,false]},baz},
...]

27. meck:new(atom(), [option()]).

28. meck:new(atom(), [option()]).

29. meck:new(atom(), [option()]).
passthrough

30. meck:new(atom(), [option()]).
no_passthrough_cover

31. meck:new(atom(), [option()]).
{stub_all, ret_spec()}

32. meck:new(atom(), [option()]).
no_link

33. meck:new(atom(), [option()]).
unstick

34. meck:new(atom(), [option()]).
no_history

35. meck:new(atom(), [option()]).
non_strict

36. meck:new(atom(), [option()]).
{spawn_opt, [any()]}

37. meck:delete(foo, bar, 1).

38. meck:unload(foo).

39. QUESTIONS?
http://github.com/eproxus/meck